Only check in lists and dictionaries

The "in" operator also works on strings which can cause problems with this line if the attribute and the object are named the same thing.

Signed-off-by: George Sibble <gsibble@gmail.com>
Check for None Type

Signed-off-by: George Sibble <gsibble@gmail.com>
Merge pull request #70 from sibblegp/fix_python_obj_type

Only check in lists and dictionaries