docs: def find(pred, items):
  	"""
  	Find the index of the first element in items for which pred returns
  	True
  
  	>>> find(lambda x: x > 3, range(100))
  	4
  	>>> find(lambda x: x < -3, range(100)) is None
  	True
  	"""
  	for i, item in enumerate(items):
  		if pred(item):
  			return i