django中ModelBase的属性

django中model类都是ModelBase的子类。ModelBase是在django.db.models.base中定义的。
如果一个mdoel类是ModelBase的子类，他的属性有：
['DoesNotExist', 'MultipleObjectsReturned', '__class__', '__delattr__', '__dict__',
'__doc__', '__eq__', '__getattribute__', '__hash__', '__init__', '__metaclass__',
'__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__',
'__setattr__', '__str__', '__unicode__', '__weakref__', '_base_manager',
'_collect_sub_objects', '_default_manager', '_deferred', '_get_FIELD_display',
'_get_next_or_previous_by_FIELD', '_get_next_or_previous_in_order', '_get_pk_val',
'_meta', '_set_pk_val', 'delete', 'objects', 'permissions', 'pk',
'prepare_database_save', 'save', 'save_base', 'serializable_value', 'user_set']


其中_meta的属性有：
['__class__', '__delattr__', '__dict__', '__doc__', '__getattribute__', '__hash__',
'__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__',
'__setattr__', '__str__', '__weakref__', '_field_cache', '_field_name_cache',
'_fields', '_fill_fields_cache', '_fill_m2m_cache', '_fill_related_many_to_many_cache',
'_fill_related_objects_cache', '_join_cache', '_m2m_cache', '_many_to_many',
'_prepare', '_related_many_to_many_cache', '_related_objects_cache', 'abstract',
'abstract_managers', 'add_field', 'add_virtual_field', 'admin', 'app_label',
'auto_field', 'concrete_managers', 'contribute_to_class', 'db_table', 'db_tablespace',
'duplicate_targets', 'fields', 'get_add_permission', 'get_all_field_names',
'get_all_related_m2m_objects_with_model', 'get_all_related_many_to_many_objects',
'get_all_related_objects', 'get_all_related_objects_with_model', 'get_ancestor_link',
'get_base_chain', 'get_change_permission', 'get_delete_permission', 'get_field',
'get_field_by_name', 'get_fields_with_model', 'get_latest_by', 'get_m2m_with_model',
'get_ordered_objects', 'get_parent_list', 'has_auto_field', 'init_name_map',
'installed', 'local_fields', 'local_many_to_many', 'managed', 'many_to_many',
'module_name', 'object_name', 'order_with_respect_to', 'ordering', 'parents',
'permissions', 'pk', 'pk_index', 'proxy', 'proxy_for_model', 'setup_pk',
'setup_proxy', 'unique_together', 'verbose_name', 'verbose_name_plural',
 'verbose_name_raw', 'virtual_fields']