Called when a column is added to a class, with arguments (cls,
connection, column_name, column_definition, changeSchema,
post_funcs). This is called after the column has been added,
and is called for each column after class creation.
The AddColumnSignal class is accessible via the
post_funcs are called with (cls, so_column_obj)
__sizeof__() -> int
size of object in memory, in bytes
Abstract classes can override this to customize issubclass().
This is invoked early on by abc.ABCMeta.__subclasscheck__().
It should return True, False or NotImplemented. If it returns
NotImplemented, the normal algorithm is used. Otherwise, it
overrides the normal algorithm (and the outcome is cached).
x.__init__(...) initializes x; see help(type(x)) for signature
for more information.