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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 unescape_single_character(match):
 """ Unescape a single escape sequence found by regular expression. :param match: Regular expression match object :rtype: str :raises: ValueError if the escape sequence is invalid """

    try:
        return DECODE_MAP[match.group(0)]
    except KeyError:
        value = match.group(0)
        if value == '\\':
            raise ValueError("Unterminated escape sequence encountered")

        raise ValueError(
            "Unrecognized escape sequence encountered: {}".format(value))