def begin_slice(self, slice_ctx):
    pass
Python only calls this when key is missing!
dataset/ETHPy150Open GoogleCloudPlatform/appengine-mapreduce/python/src/mapreduce/shard_life_cycle.py/_ShardLifeCycle.begin_slice--crossover with--dataset/ETHPy150Open plotly/plotly.py/plotly/graph_objs/graph_objs.py/PlotlyDict.__getattr__