docs: def to_dict(self, serial=False):
          '''A dictionary representing the the data of the class is returned.
          Native Python objects will still exist in this dictionary (for example,
          a ``datetime`` object will be returned rather than a string)
          unless ``serial`` is set to True.
  
          '''
          if serial:
              return dict((key, self._fields[key].to_serial(getattr(self, key)))
                          for key in list(self._fields.keys()) if hasattr(self, key))
          else:
              return dict((key, getattr(self, key)) for key in list(self._fields.keys())
                         if hasattr(self, key))