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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 to_der(self):
 """ Encodes this signature using DER Returns: bytes: The DER encoding of (self.r, self.s). """

        # Output should be:
        # 0x30 <length> 0x02 <length r> r 0x02 <length s> s
        r, s = self._canonicalize()

        total_length = 6 + len(r) + len(s)
        der = bytes([0x30, total_length - 2, 0x02, len(r)]) + r + bytes([0x02, len(s)]) + s
        return der