code: @Contract(pure = true)
      public final boolean isRunning(@NonNull final String tag) {
          final Integer id = mTaggedRequests.get(tag);
          //noinspection SimplifiableIfStatement
          if (id != null) {
              return isRunning(id);
          } else {
              return false;
          }
      }
docs: Checks if an operation with given launch tag is running.
  
  @param tag a pre-cache key of the operation launch
  @return {@code true} if the operation is running, {@code false} if it is not running, or
  there was no operation launch with the tag at all