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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 GetHTTPHeaders(self):
 """Returns the HTTP headers required for request authorization. Returns: A dictionary containing the required headers. """

    http_headers = self._adwords_client.oauth2_client.CreateHttpHeader()
    if self.enable_compression:
      http_headers['accept-encoding'] = 'gzip'

    http_headers.update(self.custom_http_headers)

    return http_headers