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)