ffmpeg-python crossfade transition for unknown number of photos - ffmpeg

Question

I want to convert a bunch of photos into a video with crossfade between them. The number of photos I am converting is variable
I am using the code from HERE to apply the crossfade:
Since the number of photos are variable I looped over all the photos in the directory and generated the -loop and also the second part ([0:v]fade=t=out:st=4:d=1[v0];):
for i in range(os.listdir('photos')):
if i == 0:
text += f'\n-loop 1 -t 60 -i photos/Image{i+1}.jpg \\\n'
text2 = '\n[0:v]fade=t=out:st=4:d=1[v0]; \\\n'
else:
text += f'-loop 1 -t 60 -i photos/Image{i+1}.jpg \\\n'
text2 += f' [{i}:v]fade=t=in:st=0:d=1,fade=t=out:st=4:d=1[v{i}]; \\\n'
#And the Subprocess part
command = f'ffmpeg \
{text} \
-filter-complex \
{text2} -map "[v]" video/out.mp4'
p = subprocess.call(command, shell=True)
But this thing didn't create any video but said this:
Use -h to get full help or, even better, run 'man ffmpeg'
The full output:
ffmpeg version git-2019-11-11-20c5f4d Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 9.2.1 (GCC) 20191010
configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt --enable-amf
libavutil 56. 35.101 / 56. 35.101
libavcodec 58. 61.100 / 58. 61.100
libavformat 58. 34.101 / 58. 34.101
libavdevice 58. 9.100 / 58. 9.100
libavfilter 7. 66.100 / 7. 66.100
libswscale 5. 6.100 / 5. 6.100
libswresample 3. 6.100 / 3. 6.100
libpostproc 55. 6.100 / 55. 6.100
Hyper fast Audio and Video encoder
usage: ffmpeg [options] [[infile options] -i infile]... {[outfile options] outfile}...
Use -h to get full help or, even better, run 'man ffmpeg'