- Don't use `isdisjoint`, as it's not available on Python < 2.6. [hannosch]
1.0a4
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- Deal gracefully with missing uid catalog entries for references. [hannosch, stefan]
1.0a3
------------------
- Speed up `getReferences` and `getBackReferences` of `Referenceable` objects. We no longer load the reference objects themselves but work directly with the information on the brains. [hannosch]
- Speed up `getTargetObject` and `getSourceObject` on reference objects. [hannosch]
1.0a2
------------------
- Support passing in a list of relationships into the `getReferences` and `getBackReferences` methods. [hannosch]