def resources_availability(self):
        """Return the percentage of availability for resources."""
        # Flatten the list.
        availabilities = list(
            chain(
                *[org.check_availability() for org in self.organizations]
            )
        )
        # Filter out the unknown
        availabilities = [a for a in availabilities if type(a) is bool]
        if availabilities:
            # Trick will work because it's a sum() of booleans.
            return round(100. * sum(availabilities) / len(availabilities), 2)
        # if nothing is unavailable, everything is considered OK
        return 100
Return the percentage of availability for resources.