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: xmlbase.rb
    path of file: ./repos/stackneveroverflow/vendor/bundle/ruby/2.3.0/gems/builder-3.2.3/lib/builder
    
    the code of the file until where you have to start completion: #!/usr/bin/env ruby

require 'builder/blankslate'

module Builder

  # Generic error for builder
  class IllegalBlockError < RuntimeError; end

  # XmlBase is a base class for building XML builders.  See
  # Build
    
    def tag!(sym, *args, &block)
      text = nil
      attrs = nil
      sym = "#{sym}:#{args.shift}" if args.first.kind_of?(::Symbol)
      sym = sym.to_sym unless sym.class == ::Symbol
      args.each do |arg|
        case arg
        when ::Hash
          attrs ||= {}
          attrs.merge!(arg)
        when nil
          attrs ||= {}
          attrs.merge!({:nil => true}) if explicit_nil_handling?
        else
          text ||= ''
          text << arg.to_s
        end
      end