def extract_counts_single(sentence, pos=False):
	"""Extract the single-edge properties from a treebank sentence.

	Args:
		`Sentence`: A sentence object.
		pos (boolean): True iff the properties should be PoS-specific.
	
	Returns:
		dict of str:(list of int): Explanation by example:
			"S#det" : [2, 0] -> An edge with the label "det" branched to the left two times.
	"""
	counts = {}
	for token in sentence:
		if token.deprel is None:
			continue
		dep_label = token.deprel.split(":")[0]
		if dep_label != "_":
			if pos:
				dep_label += "+" + token.upos
			dep_label = "S#" + dep_label
			if pos:
				pos0 = "ROOT"
				if token.head != "0":
					pos0 = sentence[token.head].upos
				dep_label = "SPOS" + dep_label[1:] + "_" + pos0
			if dep_label not in counts.keys():
				counts[dep_label] = [0, 0]
			if int(token.id) < int(token.head):
				counts[dep_label][0] += 1
			else:
				counts[dep_label][1] += 1
	return counts