from typing import List
from pydantic import BaseModel

class Foo(BaseModel):
    count: int
    size: float = None

class Bar(BaseModel):
    apple = 'x'
    banana = 'y'

class Spam(BaseModel):
    foo: Foo
    bars: List[Bar]

m = Spam(foo={'count': 4}, bars=[{'apple': 'x1'}, {'apple': 'x2'}])
print(m)
#> Spam foo=<Foo count=4 size=None>
#>      bars=[<Bar apple='x1' banana='y'>, <Bar apple='x2' banana='y'>]
print(m.dict())
#> {
#>     'foo': {'count': 4, 'size': None},
#>     'bars': [
#>         {'apple': 'x1', 'banana': 'y'},
#>         {'apple': 'x2', 'banana': 'y'}
#>     ]
#> }