code: @Override
    protected boolean isReusable(Bitmap value) {
      Preconditions.checkNotNull(value);
      return !value.isRecycled() &&
          value.isMutable();
    }
docs: Determine if this bitmap is reusable (i.e.) if subsequent {@link #get(int)} requests can
  use this value.
  The bitmap is reusable if
  - it has not already been recycled AND
  - it is mutable
  @param value the value to test for reusability
  @return true, if the bitmap can be reused