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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 ensure(arg1, arg2=None):
 """ Specify a precondition described by `description` and tested by `predicate`. """


    assert (isinstance(arg1, str) and isfunction(arg2)) or (isfunction(arg1) and arg2 is None)

    description = ""
    predicate = lambda x: x

    if isinstance(arg1, str):
        description = arg1
        predicate = arg2
    else:
        description = get_function_source(arg1)
        predicate = arg1

    return condition(description, predicate, False, True)