I am trying to implement the tutorial (example 1) provided for metaseq (https://pythonhosted.org/metaseq/example_session_run.html#example-session). Could someone please explain why this error exists and how to avoid it?

>>> if not os.path.exists('example.npz'):
...     ip_array = ip_signal.array
...         tsses_1kb,
...         bins=100,
...         processes=processes)
...     input_array = input_signal.array(
...         tsses_1kb,
...         bins=100,
...         processes=processes)
...     ip_array /= ip_signal.mapped_read_count() / 1e6
...     input_array /= input_signal.mapped_read_count() / 1e6
...     metaseq.persistence.save_features_and_arrays(
...         features=tsses,
...         arrays={'ip': ip_array, 'input': input_array}
...         prefix='example',

  File "<stdin>", line 15
    prefix='example',
         ^

Thank You!