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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_timezone(func, argname, arg):
 """Argument preprocessor that converts the input into a tzinfo object. Examples -------- <UTC> """

    if isinstance(arg, tzinfo):
        return arg
    if isinstance(arg, string_types):
        return timezone(arg)

    raise TypeError(
        "{func}() couldn't convert argument "
        "{argname}={arg!r} to a timezone.".format(
            func=_qualified_name(func),
            argname=argname,
            arg=arg,
        ),
    )