code: public Boolean isInside(DensityGrid dg)
  	{
  		Iterator<DensityGrid> dgNeighbourhood = dg.getNeighbours().iterator();
  		
  		while(dgNeighbourhood.hasNext())
  		{
  			DensityGrid dgprime = dgNeighbourhood.next();
  			if(!this.grids.containsKey(dgprime))
  			{
  				return false;
  			}
  		}
  		
  		return true;
  	}
docs: Inside Grids are defined in Definition 3.5 of Chen and Tu 2007 as:
  Consider a grid group G and a grid g ∈ G, suppose g =(j1, ··· ,jd), if g has
  neighboring grids in every dimension i =1, ·· · ,d, then g is an inside grid
  in G.Otherwise g is an outside grid in G.
  
  @param dg the density grid to label as being inside or out
  @return TRUE if g is an inside grid, FALSE otherwise