code: def get_vads_trans_id(vads_site_id, vads_trans_date):
      
      vads_trans_id = ""
      for i in range(0, 6):
          vads_trans_id += str(random.randint(0, 9))
      return vads_trans_id
docs: Returns a default value for vads_trans_id field.
  
      vads_trans_id field is mandatory. It is composed by 6 numeric
      characters that identifies the transaction. There is a unicity contraint
      between vads_site_id and vads_trans_date (the first 8 characters
      representing the transaction date).
  
      We consider the probability of having 2 identical
      generated vads_trans_id in the same day as null.