You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: params_protection.rb
    path of file: ./repos/padrino-framework/padrino-core/lib/padrino-core/application
    
    the code of the file until where you have to start completion: module Padrino
  ##
  # Padrino application module providing means for mass-assignment protection.
  #
  module ParamsProtection
    class << self
      def registered(app)
        included(app)
      end

      def included(base)
        base.send(:include, InstanceMethods)
        base.extend(ClassMethods)
      end
    end

    module ClassMethods
      ##
      # Implements filtering of url query params. Can prevent mass-assignment.
      #
      # @example
      #   post :update, :params => [:name, :email]
      #   post :update, :params => [:name, :id => Integer]
      #   post :update, :params => [:name => proc{ |v| v.reverse }]
      
    
      def filter_params!(params, allowed_params)
        params.each do |key,value|
          type = allowed_params[key]
          next if value.kind_of?(Array) && type
          case
          when type.kind_of?(Hash) && value.kind_of?(Hash)
            if key == Inflections.pluralize(key) && value.values.first.kind_of?(Hash)
              value.each do |array_index,array_value|
                value[array_index] = filter_params!(array_value, type)
              end
            else
              params[key] = filter_params!(value, type)
            end
          when type == Integer
            params[key] = value.empty? ? nil : value.to_i
          when type.kind_of?(Proc)
            params[key] = type.call(value)
          when type == true
          else
            params.delete(key)
          end