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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 timetable_tree_entry(tree_name, enclosed_processes, dependent_on=None, mx_name=None, mx_page=None):
 """ creates timetable context entry """

    assert enclosed_processes is not None and not isinstance(enclosed_processes, string_types)
    assert dependent_on is not None and not isinstance(dependent_on, string_types)

    timetable_entry = TimetableTreeEntry(tree_name=tree_name,
                                         enclosed_processes=enclosed_processes,
                                         dependent_on=dependent_on,
                                         mx_name=mx_name,
                                         mx_page=mx_page)
    return timetable_entry