public void SetFilters( 
   IEnumerable<CIMPointCloudFilter> filters
)

//Must be called on the MCT
//var pcsl = ...;
//Retrieve the available classification codes
//At 2.x - var dict = pcsl.QueryAvailableClassCodesAndLabels();
var dict = pcsl.GetAvailableClassCodesAndLabels();

//Filter out low noise and unclassified (7 and 1 respectively)
//consult https://pro.arcgis.com/en/pro-app/help/data/las-dataset/storing-lidar-data.htm
var filterDef = new PointCloudFilterDefinition()
{
  ClassCodes = dict.Keys.Where(c => c != 7 && c != 1).ToList(),
  ReturnValues = new List<PointCloudReturnType> { 
                         PointCloudReturnType.FirstOfMany }
};
//apply the filter
pcsl.SetFilters(filterDef.ToCIM());

//Must be called on the MCT
//var pcsl = ...;
var filters = pcsl.GetFilters();
PointCloudFilterDefinition fdef = null;
if (filters.Count() == 0)
{
  fdef = new PointCloudFilterDefinition()
  {
    //7 is "edge of flight line" - exclude
    ClassFlags = new List<ClassFlag> { 
       new ClassFlag(7, ClassFlagOption.Exclude) }
  };
}
else
{
  fdef = PointCloudFilterDefinition.FromCIM(filters);
  //keep any include or ignore class flags
  var keep = fdef.ClassFlags.Where(
         cf => cf.ClassFlagOption != ClassFlagOption.Exclude).ToList();
  //7 is "edge of flight line" - exclude
  keep.Add(new ClassFlag(7, ClassFlagOption.Exclude));
  fdef.ClassFlags = keep;
}
//apply
pcsl.SetFilters(fdef.ToCIM());