Add an access abstraction (only array tests work, yet)

The access abstraction will be the new way of accessing builtin objects. This way it will be easier to move that to another process

jedi/evaluate/context/iterable.py

@@ -300,7 +300,7 @@ class SequenceLiteralContext(ArrayMixin, AbstractIterable):
             for key, value in self._items():
                 for k in self._defining_context.eval_node(key):
                     if isinstance(k, compiled.CompiledObject) \
-                            and index == k.obj:
+                            and index == k.get_safe_value(default=None):
                         return self._defining_context.eval_node(value)
             raise KeyError('No key found in dictionary %s.' % self)