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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 _check_parser(parser):
 """Make sure a valid parser is passed. Parameters parser : str Raises ------ KeyError * If an invalid parser is passed """

    from pandas.core.computation.expr import _parsers

    if parser not in _parsers:
        raise KeyError('Invalid parser {parser!r} passed, valid parsers are'
                       ' {valid}'.format(parser=parser, valid=_parsers.keys()))