code: public int getAttributeSize(int index) {
          final VertexAttribute attribute = getAttribute(index);
          if (attribute == null) {
              return -1;
          }
          return attribute.getSize();
      }
docs: Returns the size of the attribute at the provided index, or -1 if none can be found.
  
  @param index The index to lookup
  @return The size of the attribute, or -1 if none can be found