@Deprecated
    public DBObject group(final GroupCommand cmd, final ReadPreference readPreference) {
        return toDBList(executor.execute(cmd.toOperation(getNamespace(), getDefaultDBObjectCodec(), retryReads), readPreference,
                getReadConcern()));
    }
@Deprecated
    public DBObject group(final GroupCommand cmd, final ReadPreference readPreference) {
        return toDBList(executor.execute(cmd.toOperation(getNamespace(), getDefaultDBObjectCodec(), retryReads), readPreference,
                getReadConcern()));
    }
@ Deprecated public DBObject group ( final GroupCommand cmd , final ReadPreference readPreference ) { return toDBList ( executor . execute ( cmd . toOperation ( getNamespace ( ) , getDefaultDBObjectCodec ( ) , retryReads ) , readPreference , getReadConcern ( ) ) ) ; }
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 cmd            the group command
@param readPreference {@link ReadPreference} to be used for this 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
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 .