# keeping it simple with just one nested request. no improvement with more added here.
      my $options =
          [
            {
              content => 'GET /gmail/v1/users/real_address@gmail.com/messages/165eb111fcf21503',
              'Content-type' => 'application/http',   # internal server error when set to 'application/json'
            },
          ];

  my $path = 'https://www.googleapis.com/batch/gmail/v1';

  # this is the call to Moo Google's lower level api_query function.
  my $res = $s->_gapi->api_query( {
      httpMethod => 'POST',
      path => $path,
      options => $options,
  });
  print Dumper $res;

# then, over in Moo::Google we do some Mojolicious stuff with our api_query call

   # build the transactor (this function is in Moo::Google
   # $headers was created earlier and contains bearer token
   # $headers->{content-type} = 'mixed/multipart';   # tried this and many other content types with no improvement
   my $tx = $self->ua->build_tx(
         uc $http_method =>$path => $headers => multipart => $options);

    my $res = $self->ua->start($tx)->res;
   return $res;

##</code><code>##

$VAR1 = bless( {
                 'req' => bless( {
                                   'method' => 'POST',
                                   'url' => bless( {
                                                     'scheme' => 'https',
                                                     'host' => 'www.googleapis.com',
                                                     'path' => bless( {
                                                                        'path' => '/batch/gmail/v1'
                                                                      }, 'Mojo::Path' )
                                                   }, 'Mojo::URL' ),
                                   'content' => bless( {
                                                         'events' => {
                                                                       'read' => [
                                                                                   sub { "DUMMY" }
                                                                                 ]
                                                                     },
                                                         'headers' => bless( {
                                                                               'headers' => {
                                                                                              'accept-encoding' => [
                                                                                                                     'gzip'
                                                                                                                   ],
                                                                                              'authorization' => [
                                                                                                                   'Bearer REAL_TOKEN_GOES_HERE'
                                                                                                                 ],
                                                                                              'user-agent' => [
                                                                                                                'Mojolicious (Perl)'
                                                                                                              ]
                                                                                            }
                                                                             }, 'Mojo::Headers' ),
                                                         'parts' => [
                                                                      bless( {
                                                                               'read' => sub { "DUMMY" },
                                                                               'events' => {
                                                                                             'read' => [
                                                                                                         $VAR1->{'req'}{'content'}{'parts'}[0]{'read'}
                                                                                                       ]
                                                                                           },
                                                                               'asset' => bless( {
                                                                                                   'content' => 'GET /gmail/v1/users/real_email@gmail.com/messages/165eb111fcf21503'
                                                                                                 }, 'Mojo::Asset::Memory' ),
                                                                               'headers' => bless( {
                                                                                                     'headers' => {
                                                                                                                    'content-type' => [
                                                                                                                                        'application/http'
                                                                                                                                      ]
                                                                                                                  }
                                                                                                   }, 'Mojo::Headers' )
                                                                             }, 'Mojo::Content::Single' )
                                                                    ]
                                                       }, 'Mojo::Content::MultiPart' )
                                 }, 'Mojo::Message::Request' )
               }, 'Mojo::Transaction::HTTP' );

##</code><code>##

$VAR1 = bless( {
                 'error' => {
                              'code' => '400',
                              'message' => 'Bad Request'
                            },
                 'events' => {},
                 'finished' => 3,
                 'message' => 'Bad Request',
                 'code' => '400',
                 'state' => 'finished',
                 'version' => '1.1',
                 'raw_size' => 757,
                 'max_line_size' => 8192,
                 'content' => bless( {
                                       'relaxed' => 1,
                                       'chunk_state' => 'finished',
                                       'post_buffer' => '',
                                       'max_buffer_size' => 262144,
                                       'raw_size' => 731,
                                       'auto_decompress' => 1,
                                       'state' => 'finished',
                                       'header_size' => 365,
                                       'chunk_len' => 0,
                                       'gz' => bless( do{\(my $o = '140714715991136')}, 'Compress::Raw::Zlib::inflateStream' ),
                                       'body' => 6,
                                       'events' => {
                                                     'read' => [
                                                                 sub { "DUMMY" }
                                                               ]
                                                   },
                                       'size' => 119,
                                       'real_size' => 119,
                                       'auto_relax' => 1,
                                       'read' => $VAR1->{'content'}{'events'}{'read'}[0],
                                       'headers' => bless( {
                                                             'headers' => {
                                                                            'date' => [
                                                                                        'Tue, 18 Sep 2018 15:04:56 GMT'
                                                                                      ],
                                                                            'x-xss-protection' => [
                                                                                                    '1; mode=block'
                                                                                                  ],
                                                                            'x-frame-options' => [
                                                                                                   'SAMEORIGIN'
                                                                                                 ],
                                                                            'content-length' => [
                                                                                                  145
                                                                                                ],
                                                                            'content-type' => [
                                                                                                'text/html; charset=UTF-8'
                                                                                              ],
                                                                            'server' => [
                                                                                          'GSE'
                                                                                        ],
                                                                            'x-content-type-options' => [
                                                                                                          'nosniff'
                                                                                                        ],
                                                                            'alt-svc' => [
                                                                                           'quic=":443"; ma=2592000; v="44,43,39,35"'
                                                                                         ],
                                                                            'cache-control' => [
                                                                                                 'private, max-age=0'
                                                                                               ],
                                                                            'expires' => [
                                                                                           'Tue, 18 Sep 2018 15:04:56 GMT'
                                                                                         ]
                                                                          },
                                                             'max_lines' => 100,
                                                             'max_line_size' => 8192,
                                                             'state' => 'finished',
                                                             'names' => {
                                                                          'x-xss-protection' => 'X-XSS-Protection',
                                                                          'alt-svc' => 'Alt-Svc',
                                                                          'x-frame-options' => 'X-Frame-Options',
                                                                          'x-content-type-options' => 'X-Content-Type-Options'
                                                                        },
                                                             'cache' => []
                                                           }, 'Mojo::Headers' ),
                                       'asset' => bless( {
                                                           'content' => '<HTML>
<HEAD>
<TITLE>Bad Request</TITLE>
</HEAD>
<BODY BGCOLOR="#FFFFFF" TEXT="#000000">
<H1>Bad Request</H1>
<H2>Error 400</H2>
</BODY>
</HTML>
',
                                                           'auto_upgrade' => 1,
                                                           'max_memory_size' => 262144
                                                         }, 'Mojo::Asset::Memory' ),
                                       'auto_upgrade' => 1,
                                       'buffer' => ''
                                     }, 'Mojo::Content::Single' ),
                 'max_message_size' => 2147483648
               }, 'Mojo::Message::Response' );

##</code><code>##

POST /batch/gmail/v1 HTTP/1.1^M
Accept-Encoding: gzip^M
Host: www.googleapis.com^M
User-Agent: Mojolicious (Perl)^M
Content-Length: 120^M
Content-Type: multipart/mixed; boundary=WHeuX^M
Authorization: Bearer REAL_TOKEN^M
^M
--WHeuX^M
Content-Type: application/http^M
^M
GET /gmail/v1/users/my_real_email@gmail.com/messages/165eb111fcf21503^M
--WHeuX--^M