code: def get_data(self, columns, type='ndarray', with_index=False):
          
  
          res = self.select_columns(columns)
          if type == 'ndarray':
              if with_index:
                  return res.reset_index().values
              else:
                  return res.values
          elif type == 'list':
              if with_index:
                  return res.reset_index().values.tolist()
              else:
                  return res.values.tolist()
          elif type == 'dataframe':
              if with_index:
                  return res.reset_index()
              else:
                  return res
docs: 获取不同格式的数据
  
          Arguments:
              columns {[type]} -- [description]
  
          Keyword Arguments:
              type {str} -- [description] (default: {'ndarray'})
              with_index {bool} -- [description] (default: {False})
  
          Returns:
              [type] -- [description]