code: def cache_param(self, value):
          '''Returns a troposphere Ref to a value cached as a parameter.'''
  
          if value not in self.cf_parameters:
              keyname = chr(ord('A') + len(self.cf_parameters))
              param = self.cf_template.add_parameter(troposphere.Parameter(
                  keyname, Type="String", Default=value, tags=self.tags
              ))
  
              self.cf_parameters[value] = param
  
          return troposphere.Ref(self.cf_parameters[value]f cache_param(self, value):
          '''Returns a troposphere Ref to a value cached as a parameter.'''
  
          if value not in self.cf_parameters:
              keyname = chr(ord('A') + len(self.cf_parameters))
              param = self.cf_template.add_parameter(troposphere.Parameter(
                  keyname, Type="String", Default=value, tags=self.tags
              ))
  
              self.cf_parameters[value] = param
  
          return troposphere.Ref(self.cf_parameters[value])
docs: Returns a troposphere Ref to a value cached as a parameter.