new_ornament: Helper to define the contents of a pillar
Description
This function is useful if your data renders differently depending on the
available width. In this case, implement the pillar_shaft() method for your
class to return a subclass of "pillar_shaft" and have the format() method
for this subclass call new_ornament(). See the implementation of
pillar_shaft.numeric() and format.pillar_shaft_decimal() for an example.