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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 is_python2_identifier(possible_identifier):
 """ Returns `True` if the given `possible_identifier` can be used as an identifier in Python 2. """

    match = _python2_identifier_re.match(possible_identifier)
    return bool(match) and not iskeyword(possible_identifier)