def get_variant_state_handle(self, variant_resource):
return None<EOL>
Get a value that indicates the state of the variant.

        This is used for resolve caching. For example, in the 'filesystem'
        repository type, the 'state' is the last modified date of the file
        associated with the variant (perhaps a package.py). If the state of
        any variant has changed from a cached resolve - eg, if a file has been
        modified - the cached resolve is discarded.

        This may not be applicable to your repository type, leave as-is if so.

        Returns:
            A hashable value.