removeClasses remove observations corresponding to
  specified class indexes
 
    subDataSet = dataSet.removeClassesByInd(classInds) returns
    a data set subDataSet containing only the observations that
    DO NOT have targets with values that corresped to the
    specified class indexes.

Help for prtDataSetClass/removeClassesByInd is inherited from superclass prtDataInterfaceCategoricalTargets