code: def unfriend friend
        run_callbacks :unfriend do
          friendships
          .where( friend_type: friend.class.name )
          .where( friend_id: friend.id )
          .first.destroy
        end
      end
docs: Removes a friend from an instance's friend's list
  
   @param [Object] friend a popular_model in this instance's friends list
  
   @example
     user = User.create name: "Justin"
     other_user = User.create name: "Jenny"
     user.befriend other_user
     user.unfriend other_user
  
     user.friends_with? other_user # => false