def gatherKeys(data):
	"""Gather all the possible keys in a list of dicts.
	(Note that voids in a particular row aren't too bad.)
	
	>>> from shared.tools.examples import complexListDict
	>>> gatherKeys(complexListDict)
	['date', 'double', 'int', 'string']
	"""
	keys = set()
	for row in data:
		keys.update(row)
	return sorted(list(keys))