class ConversionBackend(object) not working as expected

Hi,

As I was having problem with ghostscript and poppler, I wanted to try out the alternate pdf to image conversion backend . But not working as expected and I am not sure where am I going wrong. I tried the below code and its giving me an Opencv error.
" cv2.error: OpenCV(4.7.0) /io/opencv/modules/imgproc/src/color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cvtColor' ".... Code is below.
Its converting pdf to png , and giving me path (ex. png_path= /tmp/tmpop73i0dk/page-1.png)
Can someone please help ?

`import camelot as cl

class ConversionBackend(object):
def convert(self, pdf_path, png_path):
pass

pdf_path="/home/user/Downloads/foo.pdf"

obj=ConversionBackend()
tbl = cl.read_pdf(pdf_path, backend=obj)
print("tbl.n=",tbl.n)
`

Start with the custom ConversionBackend.convert method and the cl.read_pdf(..., backend=obj) call shown in the report; verify what image path and return value the backend expects. Reproduce the OpenCV !_src.empty() failure with the supplied PDF, then confirm completion by extracting the table without the error.

Written by the indexing model from the issue text.