Method "to_tone3" from "pypinyin.contrib.tone_convert" returns wrong result for "lün"

[Stefan Taubert]

运行环境

• 操作系统（Linux/macOS/Windows）：Linux
• Python 版本：3.8.10
• pypinyin 版本：0.47.1

问题描述

Method to_tone3 from pypinyin.contrib.tone_convert returns wrong result for lün5. Expected is lvn5 but it returns lv5n.
Using v instead of ü or using other tones/formats, i.e., lǘn don't work either.

问题复现步骤

from pypinyin.contrib.tone_convert import to_tone3

pinyin = to_tone3("lün5")

# next command fails because pinyin is "lv5n"
assert pinyin == "lvn5"

[Huang Huang]

@stefantaubert Thanks for reporting. I'll take a look at it.