Docs to Describe Types of Operators #198
Description
Issue
On the heels of #197, it's clear we need better documentation about the input and output types different operators accept/require. There are just four types of operators and it's not really that complicated once you understand it, but it's a major source of confusion for new users.
@markcoletti I believe we've discussed this recently, and I know you have slides on the topic, but I don't recall (or can't find) if you've drafted docs on this topic yet or not.
MWE
The MWE in #197 is an example of a case in which we'd like to be able to point people to the docs so they can understand what went wrong.
Expected Behavior
Docs explain the four types of operators (iterator-to-iterator, list-to-iterator, iterator-to-list, and list-to-list) clearly on the Operators page.
Actual Behavior
The docs talk about operators as generator functions but make no mention (unless I've missed something) of functions that receive or return lists.