header error

./test2.py:8: SyntaxWarning: name 'sessionID' is assigned to before global declaration
  global sessionID
./test2.py:9: SyntaxWarning: name 'client' is assigned to before global declaration
  global client
Traceback (most recent call last):
  File "./test2.py", line 15, in <module>
    service.login(creds)
  File "/usr/local/lib/python3.5/dist-packages/zeep/client.py", line 41, in __call__
    self._op_name, args, kwargs)
  File "/usr/local/lib/python3.5/dist-packages/zeep/wsdl/bindings/soap.py", line 110, in send
    options=options)
  File "/usr/local/lib/python3.5/dist-packages/zeep/wsdl/bindings/soap.py", line 68, in _create
    serialized = operation_obj.create(*args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/zeep/wsdl/definitions.py", line 197, in create
    return self.input.serialize(*args, **kwargs)
  File "/usr/local/lib/python3.5/dist-packages/zeep/wsdl/messages/soap.py", line 64, in serialize
    self.body.render(body, body_value)
  File "/usr/local/lib/python3.5/dist-packages/zeep/xsd/elements/element.py", line 191, in render
    self._render_value_item(parent, value, render_path)
  File "/usr/local/lib/python3.5/dist-packages/zeep/xsd/elements/element.py", line 215, in _render_value_item
    return self.type.render(node, value, None, render_path)
  File "/usr/local/lib/python3.5/dist-packages/zeep/xsd/types/complex.py", line 253, in render
    element.render(parent, element_value, child_path)
  File "/usr/local/lib/python3.5/dist-packages/zeep/xsd/elements/indicators.py", line 241, in render
    element.render(parent, element_value, child_path)
  File "/usr/local/lib/python3.5/dist-packages/zeep/xsd/elements/element.py", line 185, in render
    self.validate(value, render_path)
  File "/usr/local/lib/python3.5/dist-packages/zeep/xsd/elements/element.py", line 236, in validate
    "Missing element %s" % (self.name), path=render_path)
zeep.exceptions.ValidationError: Missing element RequestHeader (login.RequestHeader)