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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 _parse_boolean(value):
 """Coerce value into an bool. :param str value: Value to parse. :returns: bool or None if the value is not a boolean string. """

    value = value.lower()
    if value in _true_strings:
        return True
    elif value in _false_strings:
        return False
    else:
        return None