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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 _normalize_byte_sig(byte_sig: str) -> str: """Adds a leading 0x to the byte signature if it's not already there. :param byte_sig: 4-byte signature string :return: normalized byte signature string """

        if not byte_sig.startswith("0x"):
            byte_sig = "0x" + byte_sig
        if not len(byte_sig) == 10:
            raise ValueError(
                "Invalid byte signature %s, must have 10 characters", byte_sig
            )
        return byte_sig