Fix some flake8 warnings
Simplify context usage

This commit simplifies context usage and ensures that the script can
operate on objects, such as of type Experimenter, that have no inherent
group.
Switch to Attribute_Type to avoid confusion

Attribute_Type is a far more descriptive name and avoids any confusion
with the Data_Type parameter.  The only disadvantage is more typing and
everyone can use more typing. :)