from gi.repository import Gtk

model = Gtk.ListStore(int)
for i in range(10):
    model.append((i,))
filt = Gtk.TreeModelFilter(child_model=model)

# Raises an Exception, this is reasonable API given you can access rows and
# columns through filter correctly. My patch makes it possible.
filt[3][0] = 10

# How we have to do it now.
parent = filt.get_property("child-model")
parent[3][0] = 10

# Consider the case you don't know how deep your parent model is burried under
# all those filters.
parent = filt.get_property("child-model")
while isinstance(parent, Gtk.TreeModelFilter):
    parent = parent.get_property("child-model")
parent[3][0] = 10
