docs: public static Supplier<Type> receiverType() {
      return new Supplier<Type>() {
        @Override
        public Type get(VisitorState state) {
          MethodInvocationTree methodInvocation = (MethodInvocationTree) state.getPath().getLeaf();
          return ASTHelpers.getReceiverType(methodInvocation.getMethodSelect());
        }
      };
    }