code: public boolean delete(Supplier<JournalContext> journalContext, AlluxioURI uri) {
      String path = uri.getPath();
      LOG.info("Unmounting {}", path);
      if (path.equals(ROOT)) {
        LOG.warn("Cannot unmount the root mount point.");
        return false;
      }
  
      try (LockResource r = new LockResource(mWriteLock)) {
        if (mState.getMountTable().containsKey(path)) {
          // check if the path contains another nested mount point
          for (String mountPath : mState.getMountTable().keySet()) {
            try {
              if (PathUtils.hasPrefix(mountPath, path) && (!path.equals(mountPath))) {
                LOG.warn("The path to unmount {} contains another nested mountpoint {}",
                    path, mountPath);
                return false;
              }
            } catch (InvalidPathException e) {
              LOG.warn("Invalid path {} encountered when checking for nested mount point", path);
            }
          }
          mUfsManager.removeMount(mState.getMountTable().get(path).getMountId());
          mState.applyAndJournal(journalContext,
              DeleteMountPointEntry.newBuilder().setAlluxioPath(path).build());
          return true;
        }
        LOG.warn("Mount point {} does not exist.", path);
        return false;
      }
    }
docs: Unmounts the given Alluxio path. The path should match an existing mount point.
  
  @param journalContext journal context
  @param uri an Alluxio path URI
  @return whether the operation succeeded or not