code: def function_dict(self):
          
          func_dict = OrderedDict()
          for var, func in self.vars_as_functions.items():
              expr = self.model_dict[var].xreplace(self.vars_as_functions)
              func_dict[func] = expr
          return func_dict
docs: Equivalent to ``self.model_dict``, but with all variables replaced by
          functions if applicable. Sorted by the evaluation order according to
          ``self.ordered_symbols``, not alphabetical like ``self.model_dict``!