well.

The keys are supposed to be unique dotted strings.  For instance
module paths are a good choice for it.  What is stored in there is
irrelevant for the operation of click.  However what is important is
that code that places data here adheres to the general semantics of
the system.

Example usage::

    LANG_KEY = f'{__name__}.lang'

    def set_language(value):
        ctx = get_current_context()
        ctx.meta[LANG_KEY] = value

    def get_language():
        return get_current_context().meta.get(LANG_KEY, 'en_US')

.. versionadded:: 5.0
)