code: def increment_dict_val(dict_obj, key, value, zero_value=0):
      
      dict_obj[key] = dict_obj.get(key, zero_value) + value
docs: Increments the value mapped by the given key by the given val.
      If the key is missing from the dict, the given mapping is added.
  
      Parameters
      ----------
      dict_obj : dict
          The dict to increment a value in.
      key : object
          The key whose value is to be incremented.
      value : object
          The value to increment the existing mapping by.
      zero_value : object, optional
          The value added to the given value if no existing mapping is found.
          Set to 0 by default. Thus, this should be set to the corresponding
          identity element (with respect to addition) for non-numeric-valued
          dictionaries.
  
      Examples
      --------
      >>> dict_obj = {'a':2, 'b':1}
      >>> increment_dict_val(dict_obj, 'a', 4)
      >>> print(dict_obj['a'])
      6
      >>> increment_dict_val(dict_obj, 'd', 4)
      >>> print(dict_obj['d'])
      4