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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def list_models(filename):
 """ Lists all models in given filename. Parameters filename: str path to filename, where the model has been stored. Returns ------- obj: dict A mapping by name and a comprehensive description like this: """

    from .h5file import H5File
    with H5File(filename, mode='r') as f:
        return f.models_descriptive