docs: def _from_rest_blank(model, props):
      """ Set empty strings to None where allowed
  
      This is done on fields with `allow_blank=True` which takes
      an incoming empty string & sets it to None so validations
      are skipped. This is useful on fields that aren't required
      with format validations like URLType, EmailType, etc.
      """
  
      blank = model.get_fields_by_prop('allow_blank', True)
  
      for field in blank:
          try:
              if props[field] == '':
                  props[field] = None
          except KeyError:
              continue