code: private boolean allDefinitionsEquivalent(Collection<Node> definitions) {
      if (definitions.isEmpty()) {
        return true;
      }
  
      Node definition = Iterables.get(definitions, 0);
      checkArgument(definition.isFunction(), definition);
  
      return definitions.stream().allMatch((d) -> compiler.areNodesEqualForInlining(d, definition));
    }
docs: Given a set of method definitions, verify they are the same.