code: def eval(self, data, name='eval', iteration=0):
          
          self._validate_features(data)
          return self.eval_set([(data, name)], iteration)
docs: Evaluate the model on mat.
  
          Parameters
          ----------
          data : DMatrix
              The dmatrix storing the input.
  
          name : str, optional
              The name of the dataset.
  
          iteration : int, optional
              The current iteration number.
  
          Returns
          -------
          result: str
              Evaluation result string.