code: private ContractImpl getContractImpl(final Class<?> cls) throws InitializationError {
          final ContractImpl impl = cls.getAnnotation( ContractImpl.class );
          if (impl == null) {
  
              throw new InitializationError( "Classes annotated as @RunWith( ContractSuite ) [" + cls
                      + "] must also be annotated with @ContractImpl" );
          }
          return impl;
      }
docs: Get the ContractImpl annotation. Logs an error if the annotation is not
  found.
  
  @param cls
  The class to look on
  @return ContractImpl or null if not found.
  @throws InitializationError