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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 encode(self, pad=106):
 """Encodes this AIT command to binary. If pad is specified, it indicates the maximum size of the encoded command in bytes. If the encoded command is less than pad, the remaining bytes are set to zero. Commands sent to ISS payloads over 1553 are limited to 64 words (128 bytes) with 11 words (22 bytes) of CCSDS overhead (SSP 52050J, Section 3.2.3.4). This leaves 53 words (106 bytes) for the command itself. """

        opcode  = struct.pack('>H', self.defn.opcode)
        offset  = len(opcode)
        size    = max(offset + self.defn.argsize, pad)
        encoded = bytearray(size)

        encoded[0:offset] = opcode
        encoded[offset]   = self.defn.argsize
        offset           += 1
        index             = 0

        for defn in self.defn.argdefns:
            if defn.fixed:
                value = defn.value
            else:
                value  = self.args[index]
                index += 1
            encoded[defn.slice(offset)] = defn.encode(value)

        return encoded