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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 format(tokens, formatter, outfile=None):
 # pylint: disable=redefined-builtin """ Format a tokenlist ``tokens`` with the formatter ``formatter``. If ``outfile`` is given and a valid file object (an object with a ``write`` method), the result will be written to it, otherwise it is returned as a string. """

    try:
        if not outfile:
            realoutfile = getattr(formatter, 'encoding', None) and BytesIO() or StringIO()
            formatter.format(tokens, realoutfile)
            return realoutfile.getvalue()
        else:
            formatter.format(tokens, outfile)
    except TypeError as err:
        if (isinstance(err.args[0], str) and
            ('unbound method format' in err.args[0] or
             'missing 1 required positional argument' in err.args[0])):
            raise TypeError('format() argument must be a formatter instance, '
                            'not a class')
        raise