@_FFI.callback(u'Key(ExternContext*, Value*)')
def extern_key_for(context_handle, val):
 c = _FFI.from_handle(context_handle)
 return c.value_to_key(val)

@ _FFI . callback ( u'Key(ExternContext*, Value*)' ) def extern_key_for ( context_handle , val ) : c = _FFI . from_handle ( context_handle ) return c . value_to_key ( val )
return a key for a value .