Macro impl_batch_load_many 

macro_rules! impl_batch_load_many {
    ($entity:ty, $fk_type:ty, $fk_extractor:expr, $fk_column:expr) => { ... };
}

Macro to implement BatchLoadMany for has_many relationships

Example

impl_batch_load_many!(animal_photos::Entity, i32, |m| m.animal_id);