code: def check_image_is_4d(img, min_num_volumes=2):
      
  
      if len(img.shape) < 4:
          raise ValueError('Input volume must be 4D!')
      elif len(img.shape) == 4:
          for dim_size in img.shape[:3]:
              if dim_size < 1:
                  raise ValueError('Atleast one slice must exist in each dimension')
          if img.shape[3] < min_num_volumes:
              raise ValueError('Input volume is 4D '
                               'with less than {} volumes!'.format(min_num_volumes))
      elif len(img.shape) > 4:
          raise ValueError('Too many dimensions : more than 4.\n'
                           'Invalid shape of image : {}'.format(img.shape))
  
      return img
docs: Ensures the image loaded is 3d and nothing else.