get_file_name(query) -> filename -- return the filename found in a
	given, found by matching a regular expression.

def get_file_name(query):
	"""get_file_name(query) -> filename -- return the filename found in a
	given, found by matching a regular expression.
	"""
	match = re.search(r'\S*\.[\d\w]{1,4}', query)
	if(match):
		filename = match.group()
		return filename
	else:
		start = match.start()
		end = match.end()
		spaces = re.finditer(r' ', query)
		space_index = []
		for space in spaces:
			space_index.append(space.start())
		space_index.pop()
		for i in space_index:
			filename = query[i+1:end]
			if(os.path.isfile(filename)):
				return filename
		return None