<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def download(self, output="", outputFile="", silent=True):
 		"""	Downloads the image of the comic onto your computer. 			Arguments: 				output: the output directory where comics will be downloaded to. The 				default argument for 'output is the empty string; if the empty 				string is passed, it defaults to a "Downloads" directory in your home folder 				(this directory will be created if it does not exist). 				outputFile: the filename that will be written. If the empty string 				is passed, outputFile will default to a string of the form xkcd-(comic number)-(image filename), 				so for example, xkcd-1691-optimization.png. 				silent: boolean, defaults to True. If set to False, an error will be printed 				to standard output should the provided integer argument not be valid. 			Returns the path to the downloaded file, or an empty string in the event 			of failure."""

		image = urllib.urlopen(self.imageLink).read()

		#Process optional input to work out where the dowload will go and what it'll be called
		if output != "":
			output = os.path.abspath(os.path.expanduser(output))
		if output == "" or not os.path.exists(output):
			output = os.path.expanduser(os.path.join("~", "Downloads"))
			# Create ~/Downloads if it doesn't exist, since this is the default path.
			if not os.path.exists(output):
				os.mkdir(output)
		if outputFile == "":
			outputFile = "xkcd-" + str(self.number) + "-" + self.imageName

		output = os.path.join(output, outputFile)
		try:
			download = open(output, 'wb')
		except:
			if not silent:
				print("Unable to make file " + output)
			return ""
		download.write(image)
		download.close()
		return output