class ViewModel::AccessControl::Tree

def create_policy(view_name)
  policy = Class.new(Node)
  # View names are not necessarily rails constants, but we want
  # `const_set` them so they show up in stack traces.
  mangled_name = view_name.tr('.', '_')
  const_set(:"#{mangled_name}Policy", policy)
  view_policies[view_name] = policy
  policy.include_from(self::AlwaysPolicy)
  policy
end