code: public Observable<Void> deleteFirewallRuleAsync(String resourceGroupName, String accountName, String firewallRuleName) {
          return deleteFirewallRuleWithServiceResponseAsync(resourceGroupName, accountName, firewallRuleName).map(new Func1<ServiceResponse<Void>, Void>() {
              @Override
              public Void call(ServiceResponse<Void> response) {
                  return response.body();
              }
          });
      }
docs: Deletes the specified firewall rule from the specified Data Lake Store account.
  
  @param resourceGroupName The name of the Azure resource group that contains the Data Lake Store account.
  @param accountName The name of the Data Lake Store account from which to delete the firewall rule.
  @param firewallRuleName The name of the firewall rule to delete.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceResponse} object if successful.