code: @NotNull public static <T> Observable<Response<T>> from(@NotNull final ApolloCall<T> call) {
      return from(call, Emitter.BackpressureMode.BUFFER);
    }
docs: Converts an {@link ApolloCall} to a Observable with backpressure mode {@link rx.Emitter.BackpressureMode#BUFFER}.
  The number of emissions this Observable will have is based on the {@link ResponseFetcher} used with the call.
  
  @param call the ApolloCall to convert
  @param <T>  the value type
  @return the converted Observable