One problem with the "write()" method is that occasionally data looks
  like a number but you don't want it treated as a number. For example,
  zip codes or ID numbers often start with a leading zero. If you write
  this data as a number then the leading zero(s) will be stripped. You can
  change this default behaviour by using the "keep_leading_zeros()"
  method. While this property is in place any integers with leading zeros
  will be treated as strings and the zeros will be preserved. See the
  "keep_leading_zeros()" section for a full discussion of this issue.
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