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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 _content_length(line):
 """Extract the content length from an input line."""

        if line.startswith(b'Content-Length: '):
            _, value = line.split(b'Content-Length: ')
            value = value.strip()
            try:
                return int(value)
            except ValueError:
                raise ValueError("Invalid Content-Length header: {}".format(value))

        return None