function isIIFE(node) {
  return (
    node.type === 'CallExpression' && node.callee.type === 'FunctionExpression'
  )
}
Determines if a given expression node is an IIFE
@param {Expression} node The node to check
@returns {node is CallExpression & { callee: FunctionExpression } } `true` if the given node is an IIFE