title: How to dict or data check keys in pydantic
body: <pre><code>class mail(BaseModel):
      mailid: int
      email: str
      
  class User(BaseModel):
      id: int
      name: str
      mails: List[mail]
  
  data1 = {
      'id': 123,
      'name': 'Jane Doe',
      'mails':[
          {'mailid':1,'email':'aeajhs@gmail.com'}, 
          {'mailid':2,'email':'aeajhsds@gmail.com'}
      ]
  }
  userobj = User(**data1)  # Accepted
  data2 = {
          'id': 123,
          'name': 'Jane Doe',
          'mails':[
              {'mailid':1,'email':'aeajhs@gmail.com'}, 
              {'email':'aeajhsds@gmail.com'}
          ]
      }
      
  userobj = User(**data2)  # Discarded or not accepted
  </code></pre>
  <p>I want to check the keys in the dictionary that we passing to pydantic model so If the key is not present in the given dictionary I want to discard that data.
  For example in data2 in mails <code>{'email':'aeajhsds@gmail.com'}</code> data2 must be discarded</p>