def file_allowed(self, storage, basename):
return self.extension_allowed(extension(basename))<EOL>
This tells whether a file is allowed. It should return `True` if the
given `werkzeug.FileStorage` object can be saved with the given
basename, and `False` if it can't. The default implementation just
checks the extension, so you can override this if you want.

:param storage: The `werkzeug.FileStorage` to check.
:param basename: The basename it will be saved under.