docs: def sign_execute_cancellation(cancellation_params, private_key):
      """
      Function to sign the parameters required to execute a cancellation request on the Switcheo Exchange.
      Execution of this function is as follows::
  
          sign_execute_cancellation(cancellation_params=signable_params, private_key=eth_private_key)
  
      The expected return result for this function is as follows::
  
          {
              'signature': '0x65986ed2cb631d4999ce8b9c895a43f....'
          }
  
      :param cancellation_params: Parameters the Switcheo Exchange returns from the create cancellation.
      :type cancellation_params: dict
      :param private_key: The Ethereum private key to sign the deposit parameters.
      :type private_key: str
      :return: Dictionary of signed message to send to the Switcheo API.
      """
      cancellation_sha256 = cancellation_params['transaction']['sha256']
      signed_sha256 = binascii.hexlify(
          Account.signHash(cancellation_sha256, private_key=private_key)['signature']).decode()
      return {'signature': '0x' + signed_sha256}