def _check_relative_import(
        self, modnode, importnode, importedmodnode, importedasname
    ):
        """check relative import. node is either an Import or From node, modname
        the imported module name.
        """
        if not self.linter.is_message_enabled("relative-import"):
            return None
        if importedmodnode.file is None:
            return False  # built-in module
        if modnode is importedmodnode:
            return False  # module importing itself
        if modnode.absolute_import_activated() or getattr(importnode, "level", None):
            return False
        if importedmodnode.name != importedasname:
            # this must be a relative import...
            self.add_message(
                "relative-import",
                args=(importedasname, importedmodnode.name),
                node=importnode,
            )
            return None
        return None
check relative import. node is either an Import or From node, modname
        the imported module name.