Iterate over the reads on a particular genome in the bam file.
        
        Parameters
        ----------
        l : str
            A location.

def count_reads(self, l):
        """
        Iterate over the reads on a particular genome in the bam file.
        
        Parameters
        ----------
        l : str
            A location.
        """
        
        if self.__paired:
            cmd = [self.__samtools, 'view', '-c', '-f', '3', self.__bam, l]
        else:
            cmd = [self.__samtools, 'view', '-c', '-F', '4', self.__bam, l]
         
        #print(' '.join(cmd))
        stdout = subprocess.Popen(cmd, stdout=subprocess.PIPE).stdout
        
        ret = int(stdout.readline().decode('utf-8').strip())
        
        stdout.close()
    
        return ret