Fix the examples. There is misinformation: "Named functions provide fine-tuned control over arithmetic results." The whole message is out of date.

in docs/actions/#built-in-actions you write:

collect_optional - Can be used for rules of the form
Elements: Elements Element | Element | EMPTY;
Returns list;

Shouldn't that be Elements: Elements Element | EMPTY;?
This pattern is also in docs/grammar_language#zero-or-more

collect_sep_optional - Can be used for rules of the form
`Elements: Elements separator Ele

E.g. If 1000 users are in a system and we only want to allocate 10% of them to our test to minimize risk, an allocation float kwarg would be useful in order to only perform the experiment for 100 users.

control - 50 users
test_1 - 50 users