def close(self):
        """Release resources.

        Note that using this class in a with-statement will automatically call
        :meth:`close`::

            with ClientEncryption(...) as client_encryption:
                encrypted = client_encryption.encrypt(value, ...)
                decrypted = client_encryption.decrypt(encrypted)

        """
        if self._io_callbacks:
            self._io_callbacks.close()
            self._encryption.close()
            self._io_callbacks = None
            self._encryption = None
Release resources.

        Note that using this class in a with-statement will automatically call
        :meth:`close`::

            with ClientEncryption(...) as client_encryption:
                encrypted = client_encryption.encrypt(value, ...)
                decrypted = client_encryption.decrypt(encrypted)

        
stackoverflow/venv/lib/python3.6/site-packages/pymongo/encryption.py