[pyos][visualization] viz.datashade() wrong positioning of matrix elements #473

I'm not sure if something's wrong with my setup, but with viz.datashade() I am not getting the output I expect. Here's an example:

import graphblas as gb
M=gb.Matrix.from_edgelist([(0,1),(0,3),(2,3)])
gb.viz.datashade(M)

This is a 3-by-4 matrix, and this is reflected in the axes ranges ([0,3] vertical, [0,4] horizontal). However, the matrix elements only appear if I zoom out, and they're not positioned at the coordinates corresponding to their indices:

Part of: pyOpenSci/software-submission#81