build_left_outer_joins

# File activerecord/lib/active_record/relation/query_methods.rb, line 1029
    def build_left_outer_joins(manager, outer_joins)
      buckets = outer_joins.group_by do |join|
        case join
        when Hash, Symbol, Array
          :association_join
        else
          raise ArgumentError, 'only Hash, Symbol and Array are allowed'
        end
      end

      build_join_query(manager, buckets, Arel::Nodes::OuterJoin)
    end