def custom_function(func, input_files, output_file):
    """
    Calls a custom function which must create the output file.

    The custom function takes 3 parameters: ``input_files``,
    ``output_file`` and a boolean ``release``.
    """
    from .modules import utils
    return {'dependencies_fn': utils.no_dependencies, 'compiler_fn': func,
        'input': input_files, 'output': output_file, 'kwargs': {}}
