public Collection<InputOperatorImpl> getAllInputOperators() {
    return Collections.unmodifiableCollection(this.inputOperators.values());
  }
Get all {@link InputOperatorImpl}s for the graph.

@return  an unmodifiable view of all {@link InputOperatorImpl}s for the graph
samza-core/src/main/java/org/apache/samza/operators/impl/OperatorImplGraph.java