code: def p_elseif_stmt(p):
      
      if len(p) == 1:
          p[0] = node.stmt_list()
      elif len(p) == 3:
          p[0] = p[2]
      elif len(p) == 6:
          p[0] = node.if_stmt(cond_expr=p[2], then_stmt=p[4], else_stmt=p[5])
      elif len(p) == 7:
          p[0] = node.if_stmt(cond_expr=p[3], then_stmt=p[5], else_stmt=p[6])
      else:
          assert 0
docs: elseif_stmt :
                  | ELSE stmt_list_opt
                  | ELSEIF expr sep stmt_list_opt elseif_stmt
                  | ELSEIF LPAREN expr RPAREN stmt_list_opt elseif_stmt