@Nullable
    public static EndpointSelector getNodeSelector(String groupName) {
        groupName = normalizeGroupName(groupName);
        return serverGroups.get(groupName);
    }
@ Nullable public static EndpointSelector getNodeSelector ( String groupName ) { groupName = normalizeGroupName ( groupName ) ; return serverGroups . get ( groupName ) ; }
Returns the {@link EndpointSelector} for the specified case-insensitive {@code groupName}.

@return the {@link EndpointSelector}, or {@code null} if {@code groupName} has not been registered yet.