docs: def rand_indices(x, rand_attr):
      """
      Function randomly selects features without replacement. It used with random forest. Selected features must have more
      than one distinct value.
      x: numpy array - dataset
      rand_attr - parameter defines number of randomly selected features
      """
      loop = True
      indices = range(len(x[0]))
  
      while loop:
          loop = False
          # randomly selected features without replacement
          rand_list = random.sample(indices, rand_attr)
          for i in rand_list:
              if len(np.unique(x[:, i])) == 1:
                  loop = True
                  indices.remove(i)
                  if len(indices) == rand_attr - 1:
                      return -1  # all features in dataset have one distinct value
                  break
      return rand_list