code: public static int assignKeyToParallelOperator(Object key, int maxParallelism, int parallelism) {
  		return computeOperatorIndexForKeyGroup(maxParallelism, parallelism, assignToKeyGroup(key, maxParallelism));
  	}
docs: Assigns the given key to a parallel operator index.
  
  @param key the key to assign
  @param maxParallelism the maximum supported parallelism, aka the number of key-groups.
  @param parallelism the current parallelism of the operator
  @return the index of the parallel operator to which the given key should be routed.