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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 GetDecoder(cls, encoding_method):
 """Retrieves the decoder object for a specific encoding method. Args: encoding_method (str):
 encoding method identifier. Returns: Decoder: decoder or None if the encoding method does not exists. """

    encoding_method = encoding_method.lower()
    decoder = cls._decoders.get(encoding_method, None)
    if not decoder:
      return None

    return decoder()