node(at:)

If the node with the given syntaxIdentifier is a (recursive) child of this node, return the node with that identifier.

SyntaxProtocol.swift:361
func node(at syntaxIdentifier: SyntaxIdentifier) -> Syntax?

If the identifier references a node from a different tree (ie. one that has a different root ID in the SyntaxIdentifier) or if no node with the given identifier is a child of this syntax node, returns nil.