Can't see the SQLAlchemy module, what should I do?

Question

Flask

It just does not see the sqlalchemy module in the flask application (a simple blog). I tried everything, and installed different versions, and changed some names to new ones, nothing helped.
Everywhere, in all tutorials, examples, everything goes smoothly, but, as always, not with me.

PS Here is the blog code (github)
And the error screen:

Answer 1

You are not importing SQLAlchemy itself, but an extension for the flask (flask.ext.sqlalchemy) and you need to install it .
You can do it like this:
pip install Flask-SQLAlchemy

Answer 2

Try again: pip install SQLAlchemy, do a pip freeze and see what packages are installed.
The git link says:
pip install postgresql
pip install flask
pip install psycopg2
pip install flask-login

Answer 3

The link to gthub in the Readme shows the necessary manipulations to install the blog:
pip install flask-sqlalchemy
...
Have you completed them?