Matches one condition against a single fact, independently of any token.
:fun is arity 1: (fact) -> bindings_map | nil. It matches a fact of
any type, on purpose. Rete.Taxonomy's type index decides which alpha
nodes a fact reaches. This is what lets derive(:premium, :customer) make a
:premium fact reach a condition written against :customer.
Summary
Types
@type t() :: %Rete.Network.Node.Alpha{ code: atom(), fun: fun(), id: non_neg_integer() | nil, type: atom() }