message: Comment that output_shape_index can be set to negative for non-updated variables.
diff: @@ -41,6 +41,9 @@ class HloModuleConfig {
  // programs, and the caller is responsible to call the XLA-generated
  // sharding/unsharding programs before and after the sharded main program.
  //
  + // If the variable is not updated and there is not a corresponding output, use
  + // {-1} as the output_shape_index.
  + //
  // The sharding/unsharding programs will include all the input/output pairs in
  // shardable_value_update_pairs() as a flat tuple in their inputs/outputs,
  // sorted by (input_parameter_number, parameter_shape_index).
  