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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 calc_frip(self, input_bam, input_bed, threads=4):
 """ Calculate fraction of reads in peaks. A file of with a pool of sequencing reads and a file with peak call regions define the operation that will be performed. Thread count for samtools can be specified as well. :param str input_bam: sequencing reads file :param str input_bed: file with called peak regions :param int threads: number of threads samtools may use :return float: fraction of reads in peaks defined in given peaks file """

        cmd = self.simple_frip(input_bam, input_bed, threads)
        return subprocess.check_output(cmd.split(" "), shell=True)