code: def _assert_occurrence(probe, target, amount=1):
      '''
      Raise an exception, if there are different amount of specified occurrences in src.
      '''
      occ = len(probe)
      if occ > amount:
          msg = 'more than'
      elif occ < amount:
          msg = 'less than'
      elif not occ:
          msg = 'no'
      else:
          msg = None
  
      if msg:
          raise CommandExecutionError('Found {0} expected occurrences in "{1}" expression'.format(msg, target))
  
      return ocf _assert_occurrence(probe, target, amount=1):
      '''
      Raise an exception, if there are different amount of specified occurrences in src.
      '''
      occ = len(probe)
      if occ > amount:
          msg = 'more than'
      elif occ < amount:
          msg = 'less than'
      elif not occ:
          msg = 'no'
      else:
          msg = None
  
      if msg:
          raise CommandExecutionError('Found {0} expected occurrences in "{1}" expression'.format(msg, target))
  
      return occ
docs: Raise an exception, if there are different amount of specified occurrences in src.