references

# File activerecord/lib/active_record/relation/predicate_builder.rb, line 49
    def self.references(attributes)
      attributes.map do |key, value|
        if value.is_a?(Hash)
          key
        else
          key = key.to_s
          key.split('.'.freeze).first if key.include?('.'.freeze)
        end
      end.compact
    end