public Connection removeConnection(String identifier) {
        return connections.remove(identifier);
    }
Removes the connection having the given identifier from the overall map
of connections, such that it cannot be used further. This operation is
atomic.

@param identifier
    The identifier of the connection to remove.

@return
    The connection that was removed, or null if no such connection
    exists.
extensions/guacamole-auth-json/src/main/java/org/apache/guacamole/auth/json/user/UserData.java