class_docstr: Jointly trains 2 surrogate decision trees.
  Refines diff (or sim) regions by sample generation.
code: def all_same(self, y: np.ndarray):
      if isinstance(y, pd.Series):
          y = y.to_numpy()
      return (y[0] == y).all()
  
imports: import numpy
  import pandas
  from aix360.algorithms.imd.rule import Rule
label_desc: Use image node_id 6 for calling the JointSurrogateTree obj's underlying member method code with example usage: obj.all_same(y) and returns: unknown