function getRootObjectName(node) {
  if (node.type === 'Identifier') {
    return node.name
  }
  // istanbul ignore else (fallback)
  if (node.type === 'MemberExpression') {
    return getRootObjectName(node.object)
  }
}
Gets the root object name for a MemberExpression or Identifier.
@param {Node} node
@returns {string | undefined}