code: protected final void insert_at_method_start(MethodGen mg, InstructionList new_il) {
  
      // Ignore methods with no instructions
      InstructionList il = mg.getInstructionList();
      if (il == null) {
        return;
      }
      insert_before_handle(mg, il.getStart(), new_il, false);
    }
docs: Inserts an instruction list at the beginning of a method.
  
  @param mg MethodGen of method to be modified
  @param new_il InstructionList holding the new code