include?

# File activerecord/lib/active_record/associations/collection_association.rb, line 258
      def include?(record)
        klass = reflection.klass
        return false unless record.is_a?(klass)

        if loaded?
          target.include?(record)
        elsif record.new_record?
          include_in_memory?(record)
        else
          record_id = klass.composite_primary_key? ? klass.primary_key.zip(record.id).to_h : record.id
          scope.exists?(record_id)
        end
      end