--- /dev/null
+import email.message
+from email.policy import Policy
+from typing import Optional, Tuple, Union
+
+_ParamsType = Union[str, None, Tuple[str, Optional[str], str]]
+
+class MIMEBase(email.message.Message):
+ def __init__(self, _maintype: str, _subtype: str, *, policy: Policy | None = ..., **_params: _ParamsType) -> None: ...