Alternative way to detect for tmux?

[DarrienG]

Tmuxline doesn't seem to detect if tmux is running if the env var TMUX is unset. It properly applies colors to tmux, but none of the Tmuxline commands are available.

This wouldn't be a problem, except that unsetting the TMUX environment variable is required for nested tmux (which you use if you're insane like me).

In the meantime I export TMUX to be some variable when I need those commands, but it is a nuisance.