class ViewModel::ActiveRecord::UpdateOperation::MutableReferencedCollection

def insert_relative(relative_vm_ref, offset, references)
  new_members = claim_or_create_references(references)
  remove_from_members(new_members)
  index = members.find_index { |m| m.indirect_viewmodel_reference == relative_vm_ref }
  unless index
    raise ViewModel::DeserializationError::AssociatedNotFound.new(
      association_data.association_name.to_s, relative_vm_ref, blame_reference)
  end
  members.insert(index + offset, *new_members)
end