Error in running custom wrapper

[Nasir-Mahmood Abbasi]

Traceback (most recent call last):
  File "/home/arbernard/galaxy_project/galaxy/lib/galaxy/jobs/runners/__init__.py", line 170, in prepare_job
    job_wrapper.prepare()
  File "/home/arbernard/galaxy_project/galaxy/lib/galaxy/jobs/__init__.py", line 963, in prepare
    tool_evaluator.set_compute_environment( compute_environment, get_special=get_special )
  File "/home/arbernard/galaxy_project/galaxy/lib/galaxy/tools/evaluation.py", line 111, in set_compute_environment
    input_paths=compute_environment.input_paths()
  File "/home/arbernard/galaxy_project/galaxy/lib/galaxy/tools/evaluation.py", line 146, in build_param_dict
    self.__populate_output_collection_wrappers(param_dict, output_collections, output_paths, job_working_directory)
  File "/home/arbernard/galaxy_project/galaxy/lib/galaxy/tools/evaluation.py", line 335, in __populate_output_collection_wrappers
    dataset_wrapper = wrapper[ element_identifier ]
  File "/home/arbernard/galaxy_project/galaxy/lib/galaxy/tools/wrappers.py", line 405, in __getitem__
    return self.__element_instances[ key ]
  File "/home/arbernard/galaxy_project/galaxy/.venv/lib/python2.7/UserDict.py", line 40, in __getitem__
    raise KeyError(key)
KeyError: 'Normalized'

Please help.