code: def check_validity_of_long_form_args(model_obj, wide_weights, rows_to_obs):
      
      # Ensure model_obj has the necessary method for create_long_form_weights
      ensure_model_obj_has_mapping_constructor(model_obj)
      # Ensure wide_weights is a 1D or 2D ndarray.
      ensure_wide_weights_is_1D_or_2D_ndarray(wide_weights)
      # Ensure rows_to_obs is a scipy sparse matrix
      ensure_rows_to_obs_validity(rows_to_obs)
      return None
docs: Ensures the args to `create_long_form_weights` have expected properties.