I'm having a really hard time getting this to work:

pub trait RelationLoader<Node, Params>: IntoIterator {
  fn load_grouped_data(&self, conn: &PooledConnection, params: Params) -> Result<Vec<Vec<Node>>>;
}

pub trait Taggable {
  fn variant() -> TaggingVariant;
}

impl<'a, Parent: Taggable> RelationLoader<TaggingWithTag, ()> for &'a Vec<Parent>
where
  TaggingWithTag: BelongingToDsl<&'a Vec<Parent>>,
{
  fn load_grouped_data(
    &self,
    conn: &PooledConnection,
    _: (),
  ) -> Result<Vec<Vec<TaggingWithTag>>> {
    use crate::schema::tags;

    let grouped_data = TaggingWithTag::belonging_to(self)
      .inner_join(tags::table)
      .filter(taggings::type_.eq(Parent::variant().to_string()))
      .select((taggings::id, taggings::taggableId, tags::all_columns))
      .load::<TaggingWithTag>(conn)?
      .grouped_by(self);

    Ok(grouped_data)
  }
}

I'm getting this error at the inner join:

no method named `inner_join` found for associated type `<TaggingWithTag as diesel::BelongingToDsl<&'a Vec<Parent>>>::Output` in the current scope
the method `inner_join` exists but the following trait bounds were not satisfied:
`<TaggingWithTag as diesel::BelongingToDsl<&'a Vec<Parent>>>::Output: Table`
which is required by `<TaggingWithTag as diesel::BelongingToDsl<&'a Vec<Parent>>>::Output: diesel::QueryDsl`
`&<TaggingWithTag as diesel::BelongingToDsl<&'a Vec<Parent>>>::Output: Table`
which is required by `&<TaggingWithTag as diesel::BelongingToDsl<&'a Vec<Parent>>>::Output: diesel::QueryDsl`
`&mut <TaggingWithTag as diesel::BelongingToDsl<&'a Vec<Parent>>>::Output: Table`
which is required by `&mut <TaggingWithTag as diesel::BelongingToDsl<&'a Vec<Parent>>>::Output: diesel::QueryDsl`