code: def check_rna_file(rna_file):
      
      try:
          subprocess.check_output(['bedtools', '--version'])
      except OSError:
          log.error('Could not find bedtools in PATH. bedtools is required '
                    'for generating RNA coverage plot.')
          raise
      # Is this a valid BAM file? i.e., can pysam read it?
      try:
          is_bam_valid(rna_file)
      except ValueError:
          log.error('The given RNASeq BAM file is not valid')
          raise
docs: Check if bedtools is available and if the given RNA-Seq bam file is valid.