AttributeError: 'MIMEMultipart' object has no attribute 'encode'

This error occurs when you try to call the `encode` method on a `MIMEMultipart` object, which does not have this method.

To fix this error, you need to determine why you are trying to call `encode` on the `MIMEMultipart` object and find an alternative solution.

For example, if you are trying to convert the `MIMEMultipart` object to a string, you can use the `as_string` method instead of `encode`.

If you provide more context and code snippets, it will be easier to provide a more specific solution.