text: from datetime import datetime
  from typing import List, Optional
  from pydantic import BaseModel
  
  class User(BaseModel):
      id: int
      name = 'John Doe'
      signup_ts: Optional[datetime] = None
      friends: List[int] = []
  
  external_data = {
      'id': '123',
      'signup_ts': '2019-06-01 12:22',
      'friends': [1, 2, '3']
  }
  user = User(**external_data)
  print(user.id)
  print(repr(user.signup_ts))
  print(user.friends)
  print(user.dict())
  