code: function(model, cells, key, value)
  	{
  		if (cells != null && cells.length > 0)
  		{
  			model.beginUpdate();
  			try
  			{
  				for (var i = 0; i < cells.length; i++)
  				{
  					if (cells[i] != null)
  					{
  						var style = mxUtils.setStyle(model.getStyle(cells[i]), key, value);
  						model.setStyle(cells[i], style);
  					}
  				}
  			}
  			finally
  			{
  				model.endUpdate();
  			}
  		}
  	}
docs: Function: setCellStyles
  
  Assigns the value for the given key in the styles of the given cells, or
  removes the key from the styles if the value is null.
  
  Parameters:
  
  model - <mxGraphModel> to execute the transaction in.
  cells - Array of <mxCells> to be updated.
  key - Key of the style to be changed.
  value - New value for the given key.