code: @Deprecated
      public DBObject group(final DBObject key, final DBObject cond, final DBObject initial, final String reduce) {
          return group(key, cond, initial, reduce, null);
      }
docs: Group documents in a collection by the specified key and performs simple aggregation functions such as computing counts and sums.
  This is analogous to a {@code SELECT ... GROUP BY} statement in SQL.
  
  @param key     specifies one or more document fields to group
  @param cond    specifies the selection criteria to determine which documents in the collection to process
  @param initial initializes the aggregation result document
  @param reduce  specifies an $reduce function, that operates on the documents during the grouping operation
  @return a document with the grouped records as well as the command meta-data
  @mongodb.driver.manual reference/command/group/ Group Command
  @deprecated The group command was deprecated in MongoDB 3.4