public Map<CloudName, CloudAccount> cloudAccounts(Environment environment, RegionName region) {
        return zones().stream()
                      .filter(zone -> zone.concerns(environment, Optional.of(region)))
                      .findFirst()
                      .map(DeploymentSpec.DeclaredZone::cloudAccounts)
                      .orElse(cloudAccounts);
    }
Returns the cloud accounts to use for given environment and region, if any
config-model-api/src/main/java/com/yahoo/config/application/api/DeploymentInstanceSpec.java