def alias_diff(refcounts_before, refcounts_after):
    # Use -1 as default value so that any join that is created, then trimmed
    # is seen as added.
    return set(t for t in refcounts_after
               if refcounts_after[t] > refcounts_before.get(t, -1))
Testing sandboxing CommentDetailDisplayHook when
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/Django-1.6.10/django/db/models/sql/query.py/alias_diff--crossover with--dataset/ETHPy150Open reviewboard/reviewboard/reviewboard/extensions/tests.py/SandboxTests.test_email_review_comment_details