import_stmt ::= "import" module ["as" identifier] ("," module ["as" identifier])* | "from" relative_module "import" identifier ["as" identifier] ("," identifier ["as" identifier])* | "from" relative_module "import" "(" identifier ["as" identifier] ("," identifier ["as" identifier])* [","] ")" | "from" module "import" "*" module ::= (identifier ".")* identifier relative_module ::= "."* module | "."+