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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 _get_cgroup_from_proc(self, cgroup, pid, filename):
 """Find a specific cgroup file, containing metrics to extract."""

        params = {
            "file": filename,
        }
        return DockerUtil.find_cgroup_from_proc(self._mountpoints, pid, cgroup, self.docker_util._docker_root) % (params)