def AddMapping(self, filename, new_mapping):
    for field in self._REQUIRED_MAPPING_FIELDS:
      if field not in new_mapping:
        raise problems.InvalidMapping(field)
    if filename in self.GetKnownFilenames():
      raise problems.DuplicateMapping(filename)
    self._file_mapping[filename] = new_mapping
Optionally specify a formatter which will be used to format each
dataset/ETHPy150Open google/transitfeed/transitfeed/gtfsfactory.py/GtfsFactory.AddMapping--crossover with--dataset/ETHPy150Open deanhiller/databus/webapp/play1.3.x/python/Lib/logging/__init__.py/BufferingFormatter.__init__