I found a _seq method here. Here's some info:

Title : _seq
Usage : get/set seq reference
Function:
Example : $self->_seq($new_seq)
Returns : reference to underlying contained seq object
Args : (optional) new-value

sub _seq {

    my ($self,$value) = @_;
    if( defined $value) {    
    $self->{'_seqobj'} = $value;
    }
    return $self->{'_seqobj'};

}
[download]

It's probably not what you were looking for. Looking at the source, there's $self->{'_seq'} = {}; which sets up internal hashes.