observers can use syntax:
input signalname(param) to blah
param shall not be declared in that case

Useful for observers

Only one transition is executed per invokation of the observers, to
avoid triggering several times on the same continuous signal condition
(e.g. input)

This allows to cat several together...

in case a procedure is called but not defined. The parser should detect
it before. It triggers when using stop conditions because they are
declared exported and the properties.py script from the model checker
repo does not add the corresponding signal..

After exported procedure is called, execute a transition (with the same
name but no parameter) in the state machine