How to use this crate without use of struct fields

I'm relatively new to Rust so bear with me. I'm working on a project that provides a Python API to Rust code via Pyo3. In my project I'm trying to enable fast serialization and deserialization using bincode. I read this crate can mitigate the performance issues I'm seeing (bincode takes 3 times longer than serialization/deserialization with serde_json).

It's not clear to me how to take advantage of this crate when I don't use a struct field to hold the data.

For reference, this is what the unedited, actual serialization and deserialization code snippet looks like, with the Pyo3 API intact:

pub fn to_bincode(&self) -> PyResult<Vec<u8>> {
    Ok(serialize(&self).unwrap())
}
#[classmethod]
pub fn from_bincode(_cls: &PyType, encoded: Vec<u8>) -> PyResult<Self> {
    Ok(deserialize(&encoded).unwrap())
}

With the API removed, I suppose would be the analogous code:

pub fn to_bincode(&self) -> Vec<u8> {
    serialize(&self).unwrap()
}
pub fn from_bincode(encoded: Vec<u8>) -> Self {
    deserialize(&encoded).unwrap()
}

See also: https://github.com/PyO3/pyo3/issues/100

How can I utilize this crate in this case?

Start with the Rust serialization and deserialization snippets in the issue, along with the referenced PyO3 issue, and determine how this crate is intended to work when the data is not held in a struct field. Done means providing a clear, supported usage path for the shown PyO3 API or documenting why that usage is not supported.