code: def register_operators(*operators):
      
      def validate(operator):
          if isoperator(operator):
              return True
  
          raise NotImplementedError('invalid operator: {}'.format(operator))
  
      def register(operator):
          # Register operator by DSL keywords
          for name in operator.operators:
              # Check valid operators
              if name in Engine.operators:
                  raise ValueError('operator name "{}" from {} is already '
                                   'in use by other operator'.format(
                                      name,
                                      operator.__name__
                                   ))
  
              # Register operator by name
              Engine.operators[name] = operator
  
      # Validates and registers operators
      [register(operator) for operator in operators if validate(operator)]
docs: Registers one or multiple operators in the test engine.