code: def random_sample(col, n=5, filters=None):
      
      pipeline = list()
      if filters is not None:
          pipeline.append({"$match": filters})
      pipeline.append({"$sample": {"size": n}})
      return list(col.aggregate(pipeline))
docs: Randomly select n document from query result set. If no query specified,
      then from entire collection.
  
      **中文文档**
  
      从collection中随机选择 ``n`` 个样本。