astroquery.ibe's IbeClass's list_datasets not working as intended

[odysseus9672]

After applying the fix in pull request #1426 I found that the remaining list methods don't work as intended. The origin of this error seems to be that the IRSA ibe service is images only, so that level is trivial and skipped, as you can confirm by browsing the ibe schema manually. I'm proposing a fix to this issue (and the rest of the list methods) in a new pull request momentarily, where I render the list_datasets function trivial and bypass it elsewhere.

The rationale behind this approach is that I assume that the astroquery API requires the module to have the list_missions, list_datasets, and list_tables functions. If that's so, it seems that the most consistent way to satisfy this requirement is the approach proposed here.

This issue is primarily for discussion of whether this approach is the correct one, and coordinate alternate fixes, if needed.

[keflavich]

We can discuss the code in detail on that PR, but the astroquery API does not require these functions. They should not be present unless they're useful.

[odysseus9672]

The list_missions and list_tables functions are useful, list_datasets is not. Removed in current version of pull request #1430.