\var{category} argument, if given, must be a warning category class
(see above); it defaults to \exception{UserWarning}. Alternatively
\var{message} can be a \exception{Warning} instance, in which case
-\var{category} will be ignore and \code{message.__class__} will be used.
+\var{category} will be ignored and \code{message.__class__} will be used.
In this case the message text will be \code{str(message)}. This function
raises an exception if the particular warning issued is changed
into an error by the warnings filter see above. The \var{stacklevel}