def mutute_nop_jmp(instructions, index_to_mutute):
    """
    Returns a list of instructions, with one instruction mutated.
    Instruction to mutate: index_to_mutate
    nop->jmp or jmp->nop
    """
    if instructions[index_to_mutute]["operation"] == "jmp":
        instructions[index_to_mutute]["operation"] = "nop"
        return instructions
    if instructions[index_to_mutute]["operation"] == "nop":
        instructions[index_to_mutute]["operation"] = "jmp"
        return instructions
    return instructions