text: """Custom field properties functions"""
  from flask_rest_api.fields import Upload
  
  
  def uploadfield2properties(self, field, **kwargs):
      """Document Upload field properties in the API spec"""
      ret = {}
      if isinstance(field, Upload):
          if self.openapi_version.major < 3:
              ret['type'] = 'file'
          else:
              ret['type'] = 'string'
              ret['format'] = field.format
      return ret
  