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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_opcode(cls, opcode, arg=_no_arg):
 """ Create an instruction from an opcode and raw argument. Parameters opcode : int Opcode for the instruction to create. arg : int, optional The argument for the instruction. Returns ------- intsr : Instruction An instance of the instruction named by ``opcode``. """

        return type(cls)(opname[opcode], (cls,), {}, opcode=opcode)(arg)