(I'm cc'ing this to the trident users mailing list, since this is appropriate for that mailing list too.)
Right now things are a bit complicated because the development versions of yt and trident both have some backwards-incompatible changes with respect to the stable versions of yt and trident. One of those changes is how datasets are loaded, using the `load` command. The `load` command resides in yt.mods for the stable version of yt, but in yt.loaders for the development version of yt. What this means is that if you're using stable versions of trident, yt_astro_analysis, and yt, they all work together because they look for `load` in yt.mods; and if you're using the development versions of trident, yt_astro_analysis, and yt, they all work together because they look for `load` in yt.loaders. But if you mix stable and development between those codes, you'll get a conflict like what you see here.
How did you install yt and trident? Did you pip install them both? It sort of looks like you installed the development version of Trident and the stable version of yt.