@Override
      public void init(Context context) {
        String rightStoreName = joinOpSpec.getRightOpId();
        rightStreamState =
            (KeyValueStore<Object, TimestampedValue<Object>>) context.getTaskContext().getStore(rightStoreName);

        // user-defined joinFn should only be initialized once,
        // so we do it only in left partial join function and not here again.
      }
Creates a new {@link OperatorImpl} instance for the provided {@link OperatorSpec}.

@param prevOperatorSpec the original {@link OperatorSpec} that produces output for {@code operatorSpec} from {@link OperatorSpecGraph}
@param operatorSpec  the original {@link OperatorSpec} from {@link OperatorSpecGraph}
@param context  the {@link Context} required to instantiate operators
@return  the {@link OperatorImpl} implementation instance
samza-core/src/main/java/org/apache/samza/operators/impl/OperatorImplGraph.java