code: def unique_labels(line_labels):
      
      from collections import defaultdict
      d = defaultdict(int)
      for i in line_labels:
          d[i] += 1
      d = dict((i, k) for i, k in d.items() if k != 1)
      line_labels_u = []
      for lab in reversed(line_labels):
          c = d.get(lab, 0)
          if c >= 1:
              v = lab + "_num_" + str(c)
              d[lab] -= 1
          else:
              v = lab
          line_labels_u.insert(0, v)
  
      return line_labels_u
docs: If a label occurs more than once, add num. as suffix.