page_num
  
  Description:
  public int page_num (
Widget child)
  
 
  
    Finds the index of the page which contains the given child widget.
    Parameters:
    
      
        | this | 
        
           a Notebook 
         | 
      
      
        | child | 
        
           a Widget 
         | 
      
    
    Returns:
    
      
        | 
           the index of the page containing child, or  -1 if child is not in the notebook 
         |