Refactor the way builtins can be overwritten by jedi's own contexts

jedi/evaluate/stdlib.py

@@ -278,7 +278,7 @@ def collections_namedtuple(evaluator, obj, arguments):
     _fields = list(_follow_param(evaluator, arguments, 1))[0]
     if isinstance(_fields, compiled.CompiledObject):
         fields = _fields.get_safe_value().replace(',', ' ').split()
-    elif isinstance(_fields, iterable.AbstractIterable):
+    elif isinstance(_fields, iterable.Sequence):
         fields = [
             v.get_safe_value()
             for lazy_context in _fields.py__iter__()