Deprecation Warning; unclear how to fix it

I get a deprecation warning (dot syntax) for the following line
`PyCall.pycall(chart[x], PyCall.PyAny, y)`

where `x` and `y` are `Strings` and `chart` is a
`PyObject `

I tried to fixed this in numerous ways, but was not successful.

I would appreciate if someone could take a brief look (as I want to ensure that this keeps working with future PyCall versions).

an MWE (relevant line is line 91) can be found here
https://github.com/kafisatz/DecisionTrees.jl/blob/master/testing/charts_pycall_mwe.jl

The lines 100 and following are not directly relevant (but motivate my use case)

Start with the linked testing/charts_pycall_mwe.jl example, focusing on the relevant line 91 and the PyCall call shown in the issue. Run the MWE with the current PyCall version, determine why the deprecation warning occurs, and verify that the chart example works without the warning.

Vom Indexierungsmodell aus dem Issue-Text verfasst.