```ruby
class Key < ActiveRecord::Base
  include FlagShihTzu

  belongs_to :resource, polymorphic: true
  belongs_to :user, dependent: :destroy

  validates :user, presence: true
  validates :resource, presence: true

  # boolean bitfield provided by flag_shih_tzu gem
  # default false
  has_flags 1 => :can_view,
            2 => :can_edit,
            3 => :can_destroy

  # test whether a flag is set
  def can?(flag)
    self.send "can_#{flag.to_s}"
  end

  # set a flag or flags to true
  def can(*flags)
    flags.each do |flag|
      self.send "can_#{flag.to_s}=", true
    end
    self.save
  end

  # set a flag or flags to false
  def cannot(*flags)
    flags.each do |flag|
      self.send "can_#{flag.to_s}=", false
    end
    self.save
  end
end
```

Add bang to can and cannot methods
user
```ruby
class Key < ActiveRecord::Base
  include FlagShihTzu

  belongs_to :resource, polymorphic: true
  belongs_to :user, dependent: :destroy

  validates :user, presence: true
  validates :resource, presence: true

  # boolean bitfield provided by flag_shih_tzu gem
  # default false
  has_flags 1 => :can_view,
            2 => :can_edit,
            3 => :can_destroy

  # test whether a flag is set
  def can?(flag)
    self.send "can_#{flag.to_s}"
  end

  # set a flag or flags to true
  def can!(*flags)
    flags.each do |flag|
      self.send "can_#{flag.to_s}=", true
    end
    self.save
  end

  # set a flag or flags to false
  def cannot!(*flags)
    flags.each do |flag|
      self.send "can_#{flag.to_s}=", false
    end
    self.save
  end
end
```
assistant