title: How to validate more than one field of pydantic model
body: <p>I want to validate three model Fields of pydantic model. To Do this i am importing root_validator from pydantic.
  Getting below error. I found this in the <a href="https://pydantic-docs.helpmanual.io/usage/validators/#root-validators" rel="noreferrer">https://pydantic-docs.helpmanual.io/usage/validators/#root-validators</a>. Could any one help me. Find the error below.
  from pydantic import BaseModel, ValidationError, root_validator
  Traceback (most recent call last):
    File "", line 1, in 
  ImportError: cannot import name 'root_validator' from 'pydantic' (C:\Users\Lenovo\AppData\Local\Programs\Python\Python38-32\lib\site-packages\pydantic__init__.py)</p>
  
  <p>I tried in </p>
  
  <pre><code>@validator
  def validate_all(cls,v,values,**kwargs):
  </code></pre>
  
  <p>I am inheriting my pydantic model from some common fields parent model. Values showing only parent class fields, but not my child class fields. for example</p>
  
  <pre><code>class Parent(BaseModel):
      name: str
      comments: str
  class Customer(Parent):
      address: str
      phone: str
  
      @validator
      def validate_all(cls,v,values, **kwargs):
           #here values showing only (name and comment) but not address and phone.
  </code></pre>