def METHOD_NAME(self):
    class Foo(CCIDictModel):
        bar: str = None
        fields_ = Field([], alias="fields")
    class Document(CCIDictModel):
        __root__: Foo
    # JSON is YAML. Strange but true.
    foo = Document.parse_from_yaml(StringIO("{bar: 'blah'}"))
    assert type(foo) == Foo
    assert foo["fields"] == []
    foo = Document.parse_from_yaml(StringIO("{bar: 'blah', fields: [1,2]}"))
    assert foo["fields"] == [1, 2]
    foo["fields"] = ["a", "b"]
    assert foo["fields"] == ["a", "b"]