PyPDF2 is missing from output with --use-local (although installed)

[bersbersbers]

PyPDF2 is installed and I import it in my project, but when I use pipreqs --use-local, it is missing from the output, while it is included in the output of pipreqs:

user@host:~/temp> pip freeze | grep PyPDF2
PyPDF2==1.26.0

user@host:~/temp> ll
total 4
-rw-r--r-- 1 user group 38 Mar  6 12:46 my.py

user@host:~/temp> cat my.py 
import PyPDF2
print(PyPDF2._version)

user@host:~/temp> python my.py
<module 'PyPDF2._version' from '/home/user/.pyenv/versions/3.7.6/lib/python3.7/site-packages/PyPDF2/_version.py'>

user@host:~/temp> pipreqs --print
PyPDF2==1.26.0
INFO: Successfully output requirements

user@host:~/temp> pipreqs --print --use-local

INFO: Successfully output requirements

[natss]

I have the absolutely same thing with scikit-learn. pipreqs doesn't see it in the environment.

$ pip freeze | grep scikit
scikit-learn==0.23.1

$ pipreqs --print | grep scikit
INFO: Successfully output requirements
scikit_learn==0.23.1
$ pipreqs --print --use-local| grep scikit
INFO: Successfully output requirements

P.S. pipeqs is also installed in this project's enviroments .