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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def check_rna_file(rna_file):
 """Check if bedtools is available and if the given RNA-Seq bam file is valid. """

    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