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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 egress(self, envelope, http_headers, operation, binding_options):
 """Overriding the egress function to set our headers. Args: envelope: An Element with the SOAP request data. http_headers: A dict of the current http headers. operation: The SoapOperation instance. binding_options: An options dict for the SOAP binding. Returns: A tuple of the envelope and headers. """

    custom_headers = self._header_handler.GetHTTPHeaders()
    http_headers.update(custom_headers)
    return envelope, http_headers