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: dasm_listing.rb
    path of file: ./repos/grinder/node/lib/metasm/metasm/gui
    
    the code of the file until where you have to start completion: #    This file is p
    
	def keypress(key)
		case key
		when ?u	# undef data formatting with ?d
			addr = current_address
			if not @dasm.decoded[addr] and @dasm.xrefs[addr].kind_of?(Xref)
				@dasm.xrefs.delete addr
				gui_update
			end