@Override
    public void clear() {
      resources.clear();
    }
The <code>ThreadLocalPool</code> represents a {@link PoolMap.Pool} that works similarly to
{@link ThreadLocal} class. It essentially binds the resource to the thread from which it is
accessed. It doesn't remove resources when a thread exits, those resources must be closed
manually.
<p>
Note that the size of the pool is essentially bounded by the number of threads that add
resources to this pool.
</p>
@param <R> the type of the resource
hbase-client/src/main/java/org/apache/hadoop/hbase/util/PoolMap.java