from dataclasses import dataclass

@dataclass(kw_only=True)
class Token:
    pass

@dataclass(kw_only=True)
class TextToken(Token):
    text: str

@dataclass(kw_only=True)
class LinkToken(Token):
    href: str
    label: str | None = None

@dataclass(kw_only=True)
class TagToken(Token):
    tag: str

@dataclass(kw_only=True)
class MentionToken(Token):
    username: str
    uri: str | None = None