Currently it's not possible to post a question/article without a tag.
When your post is about something that no tag exists for, you can't post it.
Let's allow tag-less posts. otherwise people just select random tags
IMHO it should be a tag for every article.
If there is no tag which fits the article let's introduce the tag?
In that case, we are missing at least the following:
visualization, tools, python
Visualization, Python - will add.
And we already have the Tools tag.
Visualization and Python tags added.