function allowsAny (annotation: TypeAnnotation): boolean {
    if (annotation.type === 'TypeAnnotation' || annotation.type === 'NullableTypeAnnotation') {
      return allowsAny(annotation.typeAnnotation);
    }
    else if (annotation.type === 'AnyTypeAnnotation' || annotation.type === 'MixedTypeAnnotation') {
      return true;
    }
    else if (annotation.type === 'UnionTypeAnnotation') {
      return annotation.types.some(allowsAny);
    }
    else {
      return false;
    }
  }
Determine whether the given annotation allows any value.