Fetches a list of mountpoints.

  Args:
    only_physical: Determines whether only mountpoints for physical devices
      (e.g. hard disks) should be listed. If false, mountpoints for things such
      as memory partitions or `/dev/shm` will be returned as well.

  Returns:
    A set of mountpoints.

def _GetMountpoints(only_physical=True):
  """Fetches a list of mountpoints.

  Args:
    only_physical: Determines whether only mountpoints for physical devices
      (e.g. hard disks) should be listed. If false, mountpoints for things such
      as memory partitions or `/dev/shm` will be returned as well.

  Returns:
    A set of mountpoints.
  """
  partitions = psutil.disk_partitions(all=not only_physical)
  return set(partition.mountpoint for partition in partitions)