code: def _add_argument_register(self, reg_offset):
          
          if reg_offset in self._function_manager._arg_registers and \
                      reg_offset not in self._argument_registers:
              self._argument_registers.append(reg_offset)
docs: Registers a register offset as being used as an argument to the function.
  
          :param reg_offset:          The offset of the register to register.