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: clean_element.rb
    path of file: ./repos/stackneveroverflow/vendor/bundle/ruby/2.3.0/gems/sanitize-4.5.0/lib/sanitize/transformers
    
    the code of the file until where you have to start completion: # encoding: utf-8

require 'set'

class Sanitize; module Transformers; class CleanElement

  # Matches a valid HTML5 data attribute name. The unicode ranges included here
  # are a conservative subset of the full range of characters that are
  # technically allowed, with the intent of matching the most common characters
  # used in data attribute names while excluding uncommon or potentially
  # misleading characters, or characters with the potential to be normalized
  # into unsafe or confusing forms.
  #
    
  def call(env)
    node = env[:node]
    return if node.type != Nokogiri::XML::Node::ELEMENT_NODE || env[:is_whitelisted]

    name = env[:node_name]

    # Delete any element that isn't in the config whitelist, unless the node has
    # already been deleted from the document.
    #
    # It's important that we not try to reparent the children of a node that has
    # already been deleted, since that seems to trigger a memory leak in
    # Nokogiri.
    unless @elements.include?(name) || node.parent.nil?
      # Elements like br, div, p, etc. need to be replaced with whitespace in
      # order to preserve readability.
      if @whitespace_elements.include?(name)
        node.add_previous_sibling(Nokogiri::XML::Text.new(@whitespace_elements[name][:before].to_s, node.document))

        unless node.children.empty?
          node.add_next_sibling(Nokogiri::XML::Text.new(@whitespace_elements[name][:after].to_s, node.document))
        end
      end