from typing import Optional
from typing import Dict
from typing import Any


def compose_body(message: str, header: Optional[Dict[str, Any]] = None):
    """Prepend additional information to a message.

    :param message:
    :param header: Dict of the additional "key: value"
        entries to be prepended to the mail.

    :returns: The composed body
    """
    if not header:
        return message

    serialized_header = "\n".join(f"{k}: {v}" for k, v in header.items())

    return f"{serialized_header}\n\n{message}"