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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 _unrecognised(achr):
 """ Handle unrecognised characters. """

    if options['handleUnrecognised'] == UNRECOGNISED_ECHO:
        return achr
    elif options['handleUnrecognised'] == UNRECOGNISED_SUBSTITUTE:
        return options['substituteChar']
    else:
        raise KeyError(achr)