python: fix bindings for scc_filter as a method

* wrap/python/spot.py: Fix bindings for scc_filter.
* wrap/python/tests/remfin.py: Test them.

wrap/python/spot.py

@@ -540,9 +540,14 @@ def postprocess(automaton, *args):
 
 
 twa.postprocess = postprocess
-twa.scc_filter = scc_filter
-twa.scc_filter_states = scc_filter_states
 
+# Wrap C++-functions into lambdas so that they get converted into
+# instance methods (i.e., self passed as first argument
+# automatically), because only used-defined functions are converted as
+# instance methods.
+for meth in ('scc_filter', 'scc_filter_states'):
+    setattr(twa_graph, meth, (lambda self, *args, **kwargs:
+                              globals()[meth](self, *args, **kwargs)))
 
 # Wrapper around a formula iterator to which we add some methods of formula
 # (using _addfilter and _addmap), so that we can write things like

wrap/python/tests/remfin.py

@@ -20,8 +20,8 @@ State: 2
 """)
 aut.prop_inherently_weak()
 aut = spot.dtwa_complement(aut)
-aut = spot.scc_filter_states(aut)
-assert(aut.to_str('hoa') == """HOA: v1
+aut1 = spot.scc_filter_states(aut)
+assert(aut1.to_str('hoa') == """HOA: v1
 States: 2
 Start: 0
 AP: 1 "a"
@@ -36,6 +36,8 @@ State: 1
 [t] 1
 --END--""")
 
-assert(aut.get_name() == None)
-aut.set_name("test me")
-assert(aut.get_name() == "test me")
+assert(aut.scc_filter_states().to_str() == aut1.to_str())
+assert(aut1.get_name() == None)
+aut1.set_name("test me")
+assert(aut1.get_name() == "test me")
+# The method is the same as the function