Decrypt document with a password.

def authenticate(self, password):
        """Decrypt document with a password."""
        if self.isClosed:
            raise ValueError("operation illegal for closed doc")

        val = _fitz.Document_authenticate(self, password)

        if val: # the doc is decrypted successfully and we init the outline
            self.isEncrypted = 0
            self.initData()
            self.thisown = True


        return val