code: def num_class(x_org):
      x = x_org[~pd.isnull(x_org)]
      u = np.unique(x)
      return len(u)
  
imports: import numpy
  import pandas
  from scipy import stats
  from sklearn import preprocessing
label_desc: Use image node_id 6 for calling the PreprocessingUtils obj's underlying member method code with example usage: obj.num_class(x_org) and returns: len