class_docstr: Instance 是 fastNLP 中对应一个 sample 的类。每个 sample 在 fastNLP 中是一个 Instance 对象。
  Instance 一般与 :class:`~fastNLP.DataSet` 一起使用, Instance 的初始化如下面的代码所示::
  
      >>> instance = Instance(input="this is a demo sentence", label='good')
class_docstr_tok: ["Instance","\u662f","fastNLP","\u4e2d\u5bf9\u5e94\u4e00\u4e2a","sample","\u7684\u7c7b\u3002\u6bcf\u4e2a","sample","\u5728","fastNLP","\u4e2d\u662f\u4e00\u4e2a","Instance","\u5bf9\u8c61\u3002","Instance","\u4e00\u822c\u4e0e",":","class",":","`","~fastNLP.DataSet","`","\u4e00\u8d77\u4f7f\u7528",",","Instance","\u7684\u521d\u59cb\u5316\u5982\u4e0b\u9762\u7684\u4ee3\u7801\u6240\u793a",":",":",">",">",">","instance","=","Instance","(","input=","''","this","is","a","demo","sentence","''",",","label='good","'",")"]
code: def __init__(self, **fields):
      self.fields = fields
  
file_path: fastNLP/fastNLP/core/dataset/instance.py
imports: from typing import Mapping
  from fastNLP.core.utils.utils import pretty_table_printer
label_desc: Use image node_id 1 to create a new Instance object from inherited base classes: Mapping with example: obj = Instance()