def tally(self, name, value):
        value = value or 0  # Protection against None.
        # Start at 0 if this is the first value.
        if 'used' not in self.usages[name]:
            self.usages[name]['used'] = 0
        # Increment our usage and update the "available" metric.
        self.usages[name]['used'] += int(value)  # Fail if can't coerce to int.
        self.update_available(name)
Adds to the "used" metric for the given quota.
dataset/ETHPy150Open CiscoSystems/avos/openstack_dashboard/usage/quotas.py/QuotaUsage.tally