public ConnectionGroup removeConnectionGroup(String identifier) {
        return connectionGroups.remove(identifier);
    }
An internal method for removing a ConnectionGroup from this Directory.

@param identifier The identifier of the ConnectionGroup to remove.
@return The previous connection group for the given identifier, if found.
guacamole-ext/src/main/java/org/apache/guacamole/net/auth/simple/SimpleConnectionGroupDirectory.java