code: def sum_num_dicts(dicts, normalize=False):
      
      sum_dict = {}
      for dicti in dicts:
          for key in dicti:
              sum_dict[key] = sum_dict.get(key, 0) + dicti[key]
      if normalize:
          return norm_int_dict(sum_dict)
      return sum_dict
docs: Sums the given dicts into a single dict mapping each key to the sum
      of its mappings in all given dicts.
  
      Parameters
      ----------
      dicts : list
          A list of dict objects mapping each key to an numeric value.
      normalize : bool, default False
          Indicated whether to normalize all values by value sum.
  
      Returns
      -------
      dict
          A dict where each key is mapped to the sum of its mappings in all
          given dicts.
  
      Example
      -------
      >>> dict1 = {'a': 3, 'b': 2}
      >>> dict2 = {'a':7, 'c': 8}
      >>> result = sum_num_dicts([dict1, dict2])
      >>> print(sorted(result.items()))
      [('a', 10), ('b', 2), ('c', 8)]
      >>> result = sum_num_dicts([dict1, dict2], normalize=True)
      >>> print(sorted(result.items()))
      [('a', 0.5), ('b', 0.1), ('c', 0.4)]