Are you able to save the sparse_model? I receive the following error.

`

KeyError Traceback (most recent call last)
/tmp/ipykernel_3990/100629554.py in
----> 1 sparse_model.save('ECG-peak-detection.tf')

~/.local/lib/python3.8/site-packages/keras/utils/traceback_utils.py in error_handler(*args, **kwargs)
65 except Exception as e: # pylint: disable=broad-except
66 filtered_tb = _process_traceback_frames(e.traceback)
---> 67 raise e.with_traceback(filtered_tb) from None
68 finally:
69 del filtered_tb

~/.local/lib/python3.8/site-packages/tensorflow/python/saved_model/function_serialization.py in serialize_concrete_function(concrete_function, node_ids, coder)
65 bound_inputs.append(node_ids[capture])
66 except KeyError:
---> 67 raise KeyError(
68 f"Failed to add concrete function '{concrete_function.name}' to object-"
69 f"based SavedModel as it captures tensor {capture!r} which is unsupported"

KeyError: "Failed to add concrete function 'b'__inference_train_step_end_194526'' to object-based SavedModel as it captures tensor <tf.Tensor: shape=(), dtype=resource, value=> which is unsupported or not reachable from root. One reason could be that a stateful object or a variable that the function depends on is not assigned to an attribute of the serialized trackable object (see SaveTest.test_captures_unreachable_variable)."
`