public ConnectionGroup putConnectionGroup(ConnectionGroup connectionGroup) {
        return connectionGroups.put(connectionGroup.getIdentifier(), connectionGroup);
    }
An internal method for modifying the ConnectionGroups in this Directory.
Returns the previous connection group for the given identifier, if found.

@param connectionGroup The connection group to add or update the
                       Directory with.
@return The previous connection group for the connection group
        identifier, if found.
guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleConnectionGroupDirectory.java