code: def constants(self):
          
          constants = [ ]
          for k in self.__slots__:
              v = getattr(self, k)
              if isinstance(v, IRExpr):
                  constants.extend(v.constants)
              elif isinstance(v, IRConst):
                  constants.append(v)
          return constants
docs: A list of all of the constants that this expression ends up using.