def get_hashtag_spans(tokens):
	"""
	Finds the spans (start, end) of subtokes in a list of tokens

	Args:
		tokens: list[str]
	Returns:
		spans: list[tuple[int]]
	"""

	is_part = ["##" in t for t in tokens]
	
	spans = []
	pos_end = -1
	for pos_start, t in enumerate(is_part):
		if pos_start <= pos_end:
			continue
		if t:
			last_pos = len(is_part[pos_start:]) - 1
			for j, t_end in enumerate(is_part[pos_start:]):
				if not t_end:
					pos_end = pos_start + j
					break
				if j == last_pos:
					pos_end = pos_start + j + 1
			spans.append((pos_start, pos_end))
	
	return spans