EPP Plus - clear data validation

I'm using EPP plus library on a old version (4.5.3.3). I'm limited to it and trying to remove datavalidation from a range of values on a datasheet but can't do it - and I kept having references to it:

      foreach (var dataValiation in _package.Workbook.Worksheets[(int)DataRelationName.ImportData].DataValidations.ToList())
      {
          _package.Workbook.Worksheets[2].DataValidations.Remove(dataValiation);
      }

Also try to use "clear" but doesn't do the trick:

          var _p = _package.Workbook.Worksheets[2].Cells[5, 1, 1000, 1000];
          _p.Clear();

Also, try this:

worksheet.DataValidations.RemoveAll(x => true)

I'm completely lost on this - plus, when debugging, the count for all of datavalidations are 0 (zero) - but then, when saving the excel it appears there.

Any help?