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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def AddMapping(self, filename, new_mapping):
 """Adds an entry to the list of known filenames. Args: filename: The filename whose mapping is being added. new_mapping: A dictionary with the mapping to add. Must contain all fields in _REQUIRED_MAPPING_FIELDS. Raises: DuplicateMapping if the filename already exists in the mapping InvalidMapping if not all required fields are present """

    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