function baseInverter(object, setter, iteratee, accumulator) {
      baseForOwn(object, function(value, key, object) {
        setter(accumulator, iteratee(value), key, object);
      });
      return accumulator;
    }
The base implementation of `_.invert` and `_.invertBy` which inverts
`object` with values transformed by `iteratee` and set by `setter`.

@private
@param {Object} object The object to iterate over.
@param {Function} setter The function to set `accumulator` values.
@param {Function} iteratee The iteratee to transform values.
@param {Object} accumulator The initial inverted object.
@returns {Function} Returns `accumulator`.