GridTemplateAdorner.groupTemplateCells Method
        
 Group the specified template cells.
 
         
        Parameters
        
            - templateCells
            
 
            - 
                
Type: Array
ElementType: TemplateCellViewModel 
            - groupId
            
 
            - 
                
Type: String - May be null
(Optional) The group Id to create the group with.  
        
        Return Value
        
Type: String
        
The group ID, or null if cannot be grouped.