code: public ServiceFuture<SubnetInner> getAsync(String resourceGroupName, String virtualNetworkName, String subnetName, String expand, final ServiceCallback<SubnetInner> serviceCallback) {
          return ServiceFuture.fromResponse(getWithServiceResponseAsync(resourceGroupName, virtualNetworkName, subnetName, expand), serviceCallback);
      }
docs: Gets the specified subnet by virtual network and resource group.
  
  @param resourceGroupName The name of the resource group.
  @param virtualNetworkName The name of the virtual network.
  @param subnetName The name of the subnet.
  @param expand Expands referenced resources.
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object