code: def set_value(dct, key, value):
      
      if '.' in key:
          head, rest = key.split('.', 1)
          target = dct.setdefault(head, {})
          if not isinstance(target, dict):
              raise ValueError(
                  'Cannot set {key} in {head} '
                  'due to existing value: {target}'.format(key=key, head=head, target=target),
              )
          set_value(target, rest, value)
      else:
          dct[key] = value
docs: Set a value in a dict. If `key` contains a '.', it is assumed
      be a path (i.e. dot-delimited string) to the value's location.
  
      ::
  
          >>> d = {}
          >>> set_value(d, 'foo.bar', 42)
          >>> d
          {'foo': {'bar': 42}}