message: Add logging in autosharder
  Summary: Just add the beginning of some useful logging in the autosharder
  Test Plan: None
  Reviewers: georgep, jakeh
diff: @@ -20,6 +20,7 @@ import numpy as np
  from tensorflow.compiler.xla import xla_data_pb2
  from tensorflow.contrib.ipu.python import sharding
  from tensorflow.core.framework import attr_value_pb2
  +from tensorflow.python.platform import tf_logging as logging
  def tensor_memory_use(t):
  @@ -204,6 +205,8 @@ def automatic_sharding(num_shards,
  splitting_edges = list(
  filter(lambda e: not edge_filter(e), splitting_edges))
  + logging.debug('Possible splitting edges ' + str(splitting_edges))
  +
  # given the splitting edges found find all of the subgraphs created and order
  # them
  subgraphs, edges = find_all_subgraphs(graph_fwd, splitting_edges, input_name,
  