Function prepare_fields

pub fn prepare_fields<E, M>(
    fields: &[Field<PortableForm>],
    ext_memory: &mut E,
    registry: &M::TypeRegistry,
    checker: Checker,
) -> Result<Vec<FieldToFill>, RegistryError<E>>
where
    E: ExternalMemory,
    M: AsFillMetadata<E>,