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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def check_root(self):
        '''
        Check if the relative root path exists in the checked-out copy of the
        remote. Return the full path to that relative root if it does exist,
        otherwise return None.
        '''
        # No need to pass an environment to self.root() here since per-saltenv
        # configuration is a gitfs-only feature and check_root() is not used
        # for gitfs.
        root_dir = salt.utils.path.join(self.cachedir, self.root()).rstrip(os.sep)
        if os.path.isdir(root_dir):
            return root_dir
        log.error(
            'Root path \'%s\' not present in %s remote \'%s\', '
            'skipping.', self.root(), self.role, self.id
        )
        return None