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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 _from_bytes(bytes):
 """Takes a list of bytes, computes the checksum, and outputs the entire record as a string. bytes should be the hex record without the colon or final checksum. @param bytes list of byte values so far to pack into record. @return String representation of one HEX record """

        assert len(bytes) >= 4
        # calculate checksum
        s = (-sum(bytes)) & 0x0FF
        bin = array('B', bytes + [s])
        return ':' + asstr(hexlify(array_tobytes(bin))).upper()