code: def p_string_list(self, t):
          
  
          if len(t) == 4:
              t[0] = t[1]
              t[0].append(t[3])
          elif t[1]:
              t[0] = [t[1]]
          else:
              t[0] = []
docs: string_list : string_list COMMA STRING
                         | STRING
                         | empty