code: def frequency_to_probability(frequency_map, decorator=lambda f: f):
      
      total = sum(frequency_map.values())
      return {k: decorator(v / total) for k, v in frequency_map.items()}
docs: Transform a ``frequency_map`` into a map of probability using the sum of all frequencies as the total.
  
      Example:
          >>> frequency_to_probability({'a': 2, 'b': 2})
          {'a': 0.5, 'b': 0.5}
  
      Args:
          frequency_map (dict): The dictionary to transform
          decorator (function): A function to manipulate the probability
  
      Returns:
          Dictionary of ngrams to probability