code: function useLanguage(
    definition: SchemaDefinition,
    source: string,
    backing?: ?SchemaBacking | ?SchemaBackingConfig,
    prefix?: ?string
  ) {
    return useSchema(
      definition,
      buildSchema(source, backing),
      prefix
    );
  }
docs: Takes schema language and optional backing and creates
  a factory definition then merges that definition into the current
  @param {*} definition
  @param {*} source
  @param {*} backing
  @param {*} options