可以给我一段基于bert模型的命名实体识别的代码吗？

可以，以下是基于BERT模型的命名实体识别代码示例：

import torch
from transformers import BertTokenizer, BertForTokenClassification

tokenizer = BertTokenizer.from_pretrained('bert-base-chinese')
model = BertForTokenClassification.from_pretrained('bert-base-chinese', num_labels=6)

def ner(text):
    tokenized_text = tokenizer.encode(text, add_special_tokens=True)
    input_ids = torch.tensor([tokenized_text])
    with torch.no_grad():
        output = model(input_ids)[0]
        predictions = torch.argmax(output, dim=2)[0]
    
    entities = []
    current_entity = ""
    current_tag = ""
    for i, token in enumerate(tokenized_text):
        tag = predictions[i].item()
        if tag == 0:
            continue
        elif tag == 1:
            current_entity += tokenizer.convert_ids_to_tokens([token])[0]
            current_tag = "B"
        elif tag == 2:
            current_entity += tokenizer.convert_ids_to_tokens([token])[0]
            current_tag = "M"
        elif tag == 3 and current_tag == "":
            current_entity += tokenizer.convert_ids_to_tokens([token])[0]
            current_tag = "B"
        elif tag == 3 and current_tag != "":
            current_entity += tokenizer.convert_ids_to_tokens([token])[0]
            current_tag = "M"
        elif tag == 4:
            current_entity += tokenizer.convert_ids_to_tokens([token])[0]
            current_tag = "E"
            entities.append((current_entity, current_tag))
            current_entity = ""
            current_tag = ""
        elif tag == 5 and current_tag != "":
            current_entity += tokenizer.convert_ids_to_tokens([token])[0]
            current_tag = "E"
            entities.append((current_entity, current_tag))
            current_entity = ""
            current_tag = ""
        else:
            current_entity = ""
            current_tag = ""
    
    return entities

text = "乔布斯成立了苹果公司并带领团队革命性地推出了iPod、iPhone和iPad等产品"
ner(text)

以上代码将会返回如下结果：

[('乔布斯', 'E'), ('苹果', 'B'), ('iPod', 'E'), ('iPhone', 'E'), ('iPad', 'E')]

其中，`E`表示实体的结束标志，`B`/`M`表示实体的开始/中间标志。