I am stuck on part 2c and d. I have already written the code but there seems to be a problem with line 96 where print(validChars[i], 'count=', counts[I]) it says substring not found when I try to run it on test-high-gc-1.fastq but it works on test-small.fastq.

\# This program reads DNA sequencer output and computes statistics, such as \# the GC content. Run it from the command line like this: \# python dna_analysis.py myfile.fastq \# This program is based on Michael Ernt's assignment on DNA Analysis \#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\#\# \#\# Libraries \#\# \# The sys module supports reading files, command-line arguments, etc. import sys \#\# Read the nucleotides into a variable named seq ## \# You need to specify a file name if len( sys. argv)