code: def append_hashx_signer(self, hashx, signer_weight, source=None):
          
          return self.append_set_options_op(
              signer_address=hashx,
              signer_type='hashX',
              signer_weight=signer_weight,
              source=source)
docs: Add a HashX signer to an account.
  
          Add a HashX signer to an account via a :class:`SetOptions
          <stellar_base.operation.SetOptions` operation. This is a helper
          function for :meth:`append_set_options_op`.
  
          :param hashx: The address of the new hashX signer.
          :type hashx: str, bytes
          :param int signer_weight: The weight of the new signer.
          :param str source: The source account that is adding a signer to its
              list of signers.
          :return: This builder instance.