Dimension related problems in simple_n_dim_visualizer

Raising issue on behalf of svenson. Bug reported in google groups:

I've downloaded jupyter notebook for 3D Spectral Image example from https://pycroscopy.github.io/USID/auto_examples/plot_3D_spectral_image.html

Unfortunately, when I try to execute the following commands:
usid.plot_utils.use_nice_plot_params()
h5_main.visualize()

I got the following error:

TypeError                                 Traceback (most recent call last)
<ipython-input-7-032b56d332ff> in <module>
      1 usid.plot_utils.use_nice_plot_params()
----> 2 h5_main.visualize()

~/miniconda3/lib/python3.8/site-packages/pyUSID/io/usi_data.py in visualize(self, slice_dict, verbose, **kwargs)
   1045 
   1046         # If data has at least one dimension with 2 values in pos. AND spec., it can be visualized interactively:
-> 1047         return simple_ndim_visualizer(data_slice, pos_dims, spec_dims, verbose=verbose, **kwargs)
   1048 
   1049     def reduce(self, dims, ufunc=da.mean, to_hdf5=False, dset_name=None, verbose=False):

~/miniconda3/lib/python3.8/site-packages/sidpy/viz/jupyter_utils.py in simple_ndim_visualizer(data_mat, pos_dims, spec_dims, spec_xdim, pos_xdim, verbose)
     53         for item in parm:
     54             if not isinstance(item, Dimension):
---> 55                 raise TypeError('Expected items in {} to be of type: Dimension'.format(parm_name))
     56         if len(parm) > 2:
     57             raise NotImplementedError('Currently not able to handle more than 2 position or spectroscopic dimensions.'

TypeError: Expected items in pos_dims to be of type: Dimension

OS: Ubuntu Bionic

How the problem could be solved?

Reproduce the failure with the 3D Spectral Image example and the h5_main.visualize() call. Inspect simple_ndim_visualizer in sidpy/viz/jupyter_utils.py and its caller in usi_data.py, focusing on the expected Dimension values in pos_dims and spec_dims; done means the example visualizes without the reported TypeError.