def register_extensions(self, exts, force=False):
for ext_in, ext_out in exts.items():<EOL><INDENT>self.register_extension(ext_in, ext_out, force)<EOL><DEDENT>
Add/register extensions.

Args:
    exts (dict):
    force (bool): If ``force`` is set to ``True``, simply overwrite existing extensions, otherwise do nothing.
        If the ``logger`` is set, log a warning about the duplicate extension if ``force == False``.