instance method call

# File actionpack/lib/action_dispatch/http/permissions_policy.rb, line 36
      def call(env)
        request = ActionDispatch::Request.new(env)
        _, headers, _ = response = @app.call(env)

        return response if policy_present?(headers)

        if policy = request.permissions_policy
          headers[POLICY] = policy.build(request.controller_instance)
        end

        if policy_empty?(policy)
          headers.delete(POLICY)
        end

        response
      end