Functions for generating XML filter descriptions (<install_prefix>/share/pymango.xml).
Simply inspects all main-driver registered filter classes and accumlates the
individual XML descriptions (using the mango.application.main_driver.MainDriverFilter.getXmlFileName()
or mango.application.main_driver.MainDriverFilter.getXmlString() methods).
Helper Functions
Most of the helper functions which return a str look for the relevant method attribute
on a filter class before calling the method, if the attribute isn’t present, then None
is returned.