function _assign(/*target, ...sources*/) {
  let target = arguments[0]
  for (let i = 1, len = arguments.length; i < len; i++) {
    let source = arguments[i]
    if (source) {
      for (let prop in source) {
        if (source.hasOwnProperty(prop)) {
          target[prop] = source[prop]
        }
      }
    }
  }
  return target
}
Pseudo-polyfilled shortcut for `Object.assign`. Copies own properties from
second-and-after arguments onto the first object, overwriting any that already
exist, and returns the first argument.
@return {object}