code: public RegistryCredentialsInner getCredentials(String resourceGroupName, String registryName) {
          return getCredentialsWithServiceResponseAsync(resourceGroupName, registryName).toBlocking().single().body();
      }
docs: Gets the administrator login credentials for the specified container registry.
  
  @param resourceGroupName The name of the resource group to which the container registry belongs.
  @param registryName The name of the container registry.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @throws CloudException thrown if the request is rejected by server
  @throws RuntimeException all other wrapped checked exceptions if the request fails to be sent
  @return the RegistryCredentialsInner object if successful.