code: def arg(self, state, index, stack_base=None):
          
          session = self.arg_session
          if self.args is None:
              arg_loc = [session.next_arg(False) for _ in range(index + 1)][-1]
          else:
              arg_loc = self.args[index]
  
          return arg_loc.get_value(state, stack_base=stack_base)
docs: Returns a bitvector expression representing the nth argument of a function.
  
          `stack_base` is an optional pointer to the top of the stack at the function start. If it is not
          specified, use the current stack pointer.
  
          WARNING: this assumes that none of the arguments are floating-point and they're all single-word-sized, unless
          you've customized this CC.