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: magic_envelope.rb
    path of file: ./repos/diaspora_federation/lib/diaspora_federation/salmon
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module DiasporaFederation
  module Salmon
    # Represents a Magic Envelope for diaspora* federation messages
    #
    # When generating a Magic Envelope, 
    
      def self.unenvelop(magic_env, sender=nil, cipher_params=nil)
        raise ArgumentError unless magic_env.instance_of?(Nokogiri::XML::Element)

        validate_envelope(magic_env)
        validate_type(magic_env)
        validate_encoding(magic_env)
        validate_algorithm(magic_env)

        sender ||= sender(magic_env)
        raise InvalidSignature unless signature_valid?(magic_env, sender)

        data = read_and_decrypt_data(magic_env, cipher_params)

        logger.debug "unenvelop message from #{sender}:\n#{data}"

        xml = Nokogiri::XML(data).root
        new(Entity.entity_class(xml.name).from_xml(xml), sender)
      end