asNonNullableMap<T> method
Returns the content of this snapshot as a non-nullable map with value objects of type T.
The content should be a map and the value items of the map should be convertible to objects of type T.
The returned map is cached and unmodifiable.
Implementation
Map<String, T> asNonNullableMap<T>({String? format}) {
if (value == null) throw TypeError();
return asMap(format: format) as Map<String, T>;
}