prevent certain operations on collections when using different sessions and/or schemas

[rkoschmitzky]

Goal

Certain operations should be prevented between collections if those are using different session objects and/or schemas.

Motivation

As each session maintains its own cache we need to prevent the creation of collections that are based on different sessions. The same is true for different user-provided schemas, as these are driving the attribute resolution.

The following methods need to consider a check:

• __setattr__ (also used by apply)
• union
• difference
• symmetric_difference
• intersection