Interface to handle the outputs from the calls to any
function that causes the underlying AMPL interpreter to display a message.
If an application needs to
implement customised output handling, it must implement this interface and
then register an instance with the AMPL API using the
Note that errors and warnings are not passed through this interface,
ErrorHandler for more information.
This method is called when AMPL sends some output derived from
executing a statement.
kind: kind of the output of the AMPL interpreter.
msg: text of the output by the AMPL interpreter.