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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_value(value):
 """Unescape a value."""

    def unescape(c):
        return {
            "\\\\": "\\",
            "\\\"": "\"",
            "\\n": "\n",
            "\\t": "\t",
            "\\b": "\b",
            }[c.group(0)]
    return re.sub(r"(\\.)", unescape, value)