# File lib/fog/aws/requests/ecs/list_task_definition_families.rb, line 27
        def list_task_definition_families(params={})
          response = Excon::Response.new
          response.status = 200

          family_prefix = params['familyPrefix']

          if family_prefix
            result = self.data[:task_definitions].select do |t|
              t['family'].match(/^#{family_prefix}/)
            end
          else
            result = self.data[:task_definitions].dup
          end
          result.map! { |t| t['family'] }
          result.uniq!

          response.body = {
            'ListTaskDefinitionFamiliesResult' => {
              'families' => result
            },
            'ResponseMetadata' => {
              'RequestId' => Fog::AWS::Mock.request_id
            }
          }
          response
        end