An Elixir function with a Python signature, for a global, filter or test that takes keyword arguments.

greet = Otera.Function.new("greet", ["name", {"punctuation", "!"}], fn name, punctuation ->
  "Hello, " <> name <> punctuation
end)

Otera.render("{{ greet('Ann', punctuation='?') }}", %{}, globals: %{"greet" => greet})
#=> {:ok, "Hello, Ann?"}

A param is a name for a required argument, or {name, default}. Otera binds the positional and keyword arguments of a call to the params like a Python call, and calls fun with one value for each param. A wrong call raises the TypeError of Python, with name in the message. For a filter or a test, the first param is the value.

A plain Elixir function gets the positional arguments only.