TODO
.. seealso:: **Tasks:** - :ref:`add_custom_data` - :ref:`modify_extended_data` - :ref:`delete_extended_data` **Tutorials:** - :ref:`tut_custom_data` **Basics:** - :ref:`xdata_internals` - :ref:`extension_dictionary` - :ref:`dxf_tags_internals` **Classes:** - :class:`ezdxf.entities.xdata.XData` - :class:`ezdxf.entities.xdict.ExtensionDict` - :class:`ezdxf.entities.XRecord` - :class:`ezdxf.entities.Dictionary` - :class:`ezdxf.entities.DictionaryVar` **Helper-Classes:** - :class:`ezdxf.entities.xdata.XDataUserList` - :class:`ezdxf.entities.xdata.XDataUserDict` - :class:`ezdxf.urecord.UserRecord` - :class:`ezdxf.urecord.BinaryRecord`