code: def config_schema(self):
          
          from rez.config import _plugin_config_dict
          d = _plugin_config_dict.get(self.type_name, {})
  
          for name, plugin_class in self.plugin_classes.iteritems():
              if hasattr(plugin_class, "schema_dict") \
                      and plugin_class.schema_dict:
                  d_ = {name: plugin_class.schema_dict}
                  deep_update(d, d_)
          return dict_to_schema(d, required=True, modifier=expand_system_vars)
docs: Returns the merged configuration data schema for this plugin
          type.