QGIS plugin external libraries in plugin’s directory

Question

I’m developing my first QGIS plugin and I have to use two external libraries not included in the default OSGeoW64 installation: Couchdb and Pandas.

I would like to include those libraries in my plugin’s directory so that users don’t have to deal with the installation of them.

So I created a folder called lib, inserted in it an empty _init_.py and downloaded in it the libraries using pip:

python3 -m pip install -t lib couchdb

The directory looks like this:

mhyconos
|--- lib
     |--- bin
     |--- couchdb 
     |--- CouchDB-1.2.dist-info
     |--- _init_.py
|--- _init_.py
|--- mhyconos.py
... 

In mhyconos.py I imported couchdb using

from lib import couchdb 

but when I install the plugin, this is what happens:

What am I doing wrong?