@Override
  public Object terminate() {
    double sum = ((Number) super.terminate()).doubleValue();
    double result = sum / count;
    return downCast(result);
  }
Takes the input of data received from bucket nodes. The data is of the form of two element
array. The first element is the number of values, while the second element is the sum of the
values.
geode-core/src/main/java/org/apache/geode/cache/query/internal/aggregate/AvgPRQueryNode.java