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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 DeregisterPathSpec(cls, path_spec_type):
 """Deregisters a path specification. Args: path_spec_type (type):
 path specification type. Raises: KeyError: if path specification is not registered. """

    type_indicator = path_spec_type.TYPE_INDICATOR
    if type_indicator not in cls._path_spec_types:
      raise KeyError(
          'Path specification type: {0:s} not set.'.format(type_indicator))

    del cls._path_spec_types[type_indicator]

    if type_indicator in cls._system_level_type_indicators:
      del cls._system_level_type_indicators[type_indicator]