def visit_value(self, value, producer_node):
    pass
Called when serializing of an object starts.
dataset/ETHPy150Open GoogleCloudPlatform/DataflowPythonSDK/google/cloud/dataflow/pipeline.py/PipelineVisitor.visit_value--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/core/serializers/base.py/Serializer.start_object