import json

class Attachment:
    def __init__(self, filename: str, data: str):
        self.filename = filename
        self.data = data


class Message:
    def __init__(self, message_id: str, body: Optional[str], attachments: Optional[List[Attachment]], company: str):
        self.id = message_id
        self.body = body
        self.attachments = attachments
        self.company = company

    def to_json(self):
        return {
            "id": self.id,
            "body": self.body,
            "attachments": [attachment.__dict__ for attachment in self.attachments] if self.attachments else None,
            "company": self.company
        }