references

# File activerecord/lib/active_record/relation/predicate_builder.rb, line 32
    def self.references(attributes)
      attributes.each_with_object([]) do |(key, value), result|
        if value.is_a?(Hash)
          result << Arel.sql(key)
        elsif key.include?(".")
          result << Arel.sql(key.split(".").first)
        end
      end
    end