Abstract interface for generating an expression context.
You need to implement this interface in a class and register this class with
This is used for example in
QgsFieldExpressionWidgetclasses which will ask for a new
QgsExpressionContextevery time the expression editor is opened. This way they are able to provide an up-to-date expression editor even when the environment changes.
This method needs to be reimplemented in all classes which implement this interface and return an expression context.