docs: def request_signature(self):
          """
          The signature passed in the request.
          """
          signature = self.query_parameters.get(_x_amz_signature)
          if signature is not None:
              signature = signature[0]
          else:
              signature = self.authorization_header_parameters.get(_signature)
              if signature is None:
                  raise AttributeError("Signature was not passed in the request")
              
          return signature