def to_instances(records)
      records.each_with_object({}) do |attributes, memo|
        record = @klass.new(attributes)
        memo[record[@klass.masterman.primary_key]] = record
      end
    end
def to_instances(records)
      records.each_with_object({}) do |attributes, memo|
        record = @klass.new(attributes)
        memo[record[@klass.masterman.primary_key]] = record
      end
    end
[{ primary_key => instance, primary_key => instance, ... }]