2 small fixes: in NdArrayResolver and changeAttrExpression

Maybe it is also a good idea to add in DefaultResolver some logic for additional dictionary values evaluation in case of class has '\_\_getitem\_\_' method. 
Humm, I don't think this can actually be done.

Consider the case:
```python
class MyClass(object):
    
    def __init__(self):
        self._dct = {'bar':'foo'}
    
    def __getitem__(self, key):
        return self._dct[key]

c = MyClass()
```

__getitem__ isn't really something which accepts ints, so, trying to access its items will actually give an exception when trying to get the contents of that instance...

I'm not sure there's an approach which'd work in that case.