code: public Observable<DnsNameAvailabilityResultInner> checkDnsNameAvailabilityAsync(String location, String domainNameLabel) {
          return checkDnsNameAvailabilityWithServiceResponseAsync(location, domainNameLabel).map(new Func1<ServiceResponse<DnsNameAvailabilityResultInner>, DnsNameAvailabilityResultInner>() {
              @Override
              public DnsNameAvailabilityResultInner call(ServiceResponse<DnsNameAvailabilityResultInner> response) {
                  return response.body();
              }
          });
      }
docs: Checks whether a domain name in the cloudapp.azure.com zone is available for use.
  
  @param location The location of the domain name.
  @param domainNameLabel The domain name to be verified. It must conform to the following regular expression: ^[a-z][a-z0-9-]{1,61}[a-z0-9]$.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the DnsNameAvailabilityResultInner object