code: public <T extends CacheSpec<K, V>> T initialCapacity(int initialCapacity) {
        checkArgument(initialCapacity > 0, "Capacity must be > 0");
        this.initialCapacity = initialCapacity;
        return Cast.as(this);
     }
docs: Sets the initial capacity
  
  @param <T>             the type parameter
  @param initialCapacity The initial capacity
  @return This Cache spec