def gtf_or_db(fname):
	"""
	Determine if a file is GTF or TALON DB.

	Parameters:
		fname (str): File name / location

	Returns:
		ftype (str): 'gtf' or 'db' depending on results
	"""
	ext = fname.split('.')[-1]
	if ext == 'gtf': return 'gtf'
	elif ext == 'db': return 'db'
	else:
		raise Exception('File type must be gtf or db. '
			'Type received is {}'.format(ext))