code: def step_count(group_idx):
      
      cmp_pos = 0
      steps = 1
      if len(group_idx) < 1:
          return 0
      for i in range(len(group_idx)):
          if group_idx[cmp_pos] != group_idx[i]:
              cmp_pos = i
              steps += 1
      return steps
docs: Return the amount of index changes within group_idx.