def line_text(*fields, **kargs):
	"""
	Transform a list of values into a tsv line
	:param fields: list of values as parameters
	:param kargs: optional arguments: null_value: value to interpret as None
	:return: tsv line text
	"""
	null_value = kargs.get("null_value", "")
	return "\t".join([str(x) if x is not None else null_value for x in fields]) + "\n"