code: def increment_nested_val(dict_obj, key_tuple, value, zero_value=0):
      
      inc_val = value + safe_nested_val(
          key_tuple=key_tuple,
          dict_obj=dict_obj,
          default_value=zero_value,
      )
      put_nested_val(
          dict_obj=dict_obj,
          key_tuple=key_tuple,
          value=inc_val,
      )
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 outer-most dict to increment a value in.
      key_tuple : tuple
          The keys mapping to the nested value to increment, in order.
      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': {'g': 5}}
      >>> increment_nested_val(dict_obj, ('b', 'g'), 4)
      >>> print(dict_obj['b']['g'])
      9
      >>> increment_nested_val(dict_obj, ('b', 'z'), 17)
      >>> print(dict_obj['b']['z'])
      17