[Python] How do I resolve "No module named 'frontend'" error message?

I have installed PymuPDF/fitz because am trying to extract images from PDF files. However, upon running the code below, I am seeing No module named 'frontend'.

doc = fitz.open(pdf_path)
for i in range(len(doc)):
for img in doc.getPageImageList(i):
xref = img[0]
pix = fitz.Pixmap(doc, xref)
if pix.n < 5: # this is GRAY or RGB
pix.writePNG("p%s-%s.png" % (i, xref))
else: # CMYK: convert to RGB first
pix1 = fitz.Pixmap(fitz.csRGB, pix)
pix1.writePNG("p%s-%s.png" % (i, xref))
pix1 = None
pix = None


I have searched but there isn't single report of this kind of error. I have installed PyMuPDF, muPDF and fitz modules

Here is the error in full:

Traceback (most recent call last):
File "/home/waqar/PycharmProjects/predator/ExtractFileImage.py", line 1, in <module>
import fitz
File "/home/waqar/anaconda3/envs/retinanet/lib/python3.6/site-packages/fitz/__init__.py", line 1, in <module>
from frontend import *
ModuleNotFoundError: No module named 'frontend'

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