I am reopening an issue which was previously demoted to a question but turns out to be a shortcoming of the pythonnet API. As the discussion #1772 shows, there is no way to successfully call the function numpy.gradient(f, *varargs, axis=None, edge_order=1) as documented here: https://numpy.org/doc/stable/reference/generated/numpy.gradient.html

Here is an example in python

>>> import numpy as np
>>> dx=4.0
>>> dy=5.0
>>> zX=[[1,2,3],[4,5,6],[8,9,0]]
>>> np.gradient(zX, dx, dy)
[array([[ 0.75 ,  0.75 ,  0.75 ],
       [ 0.875,  0.875, -0.375],
       [ 1.   ,  1.   , -1.5  ]]), array([[ 0.2,  0.2,  0.2],
       [ 0.2,  0.2,  0.2],
       [ 0.2, -0.8, -1.8]])]
>>>

Various ways to call the function have been tried in #1772 but none work. This should be considered a bug.