Feels like extensions tend to make it hard to find out what you need to import to make things work as intended. Maybe visual studio proper is better at inference for it? Will only autocomplete methods that are actually in scope as far as I can tell.
If you use VS for Mac its under Preferences > Text Editor > Intellisense > Show Import Items
Better yet, if it's from a NuGet package, it'll offer to install one (or several, if there are multiple candidates).
using System.Linq;
foo.Select(x => bar);
from itertools import *
imap(foo, lambda x: bar)