Solved by ptrblck in post #5 
              
              
                An example would be to pass a valid image path as a string: 
img = cv2.imread('/tmp/image.jpeg')

Right now df_row['building_label_path'] is an np.float64 value, which is a floating point value and not a path string so you would check your df_row content and make sure to index the right column/row.