'Get Process Instance Variable' does not unwrap Java variables

[Noordsestern]

Test Data:

A process instance with a JSON variable

When getting variables from a process instance, the variable values are deserialized at Camunda side, leading to werid errors in python.

This seems to work

    @keyword("Get Process Instance Variable", tags=['process'])
    def get_process_instance_variable(self, process_instance_id: str, variable_name: str):
        """
        Returns the variable with the given name from the process instance with
        the given process_instance_id.

        Parameters:
            - ``process_instance_id``: ID of the target process instance
            - ``variable_name``: name of the variable to read

        == Example ==
        | ${variable} | Get Process Instance Variable |
        | ...         | process_instance_id=fcab43bc-b970-11eb-be75-0242ac110002 |
        | ...         | variable_name=foo |

        See also:
        https://docs.camunda.org/manual/7.5/reference/rest/process-instance/variables/get-single-variable/
        """
        with self._shared_resources.api_client as api_client:
            api_instance: ProcessInstanceApi = openapi_client.ProcessInstanceApi(api_client)

            try:
                response = api_instance.get_process_instance_variable(
                    id=process_instance_id, var_name=variable_name, deserialize_value=False)
            except ApiException as e:
                raise ApiException(f'Failed to get variable {variable_name} from '
                             f'process instance {process_instance_id}:\n{e}')
        return CamundaResources.convert_variable_dto(response)