mesos/spark — pull request #396 by JoshRosen (2013-01-22 06:36:29+00:00)
Title: Make PySpark AccumulatorParam an abstract base class

This commit makes AccumulatorParam an abstract base class, using the [abc](http://docs.python.org/2/library/abc.html) module. This allows us to use epydoc to document this interface. I also fixed an epydoc formatting issue in SparkContext.accumulate().