Misidentifying subclass of (python) list?

I'm trying to wrap a package that defines a class that subtypes python's list and adds methods. When I create one of these, it appears to be misidentified as a list, so the additional methods are not available.

The offending line seems to be conversions.jl:762:

        # only handle PyList for now
        return pyisinstance(o, @pyglobalobj :PyList_Type) ? Array : Union{}

Would it break things to check if type(o) == list rather than whether it's an instance?

Example:

Main> py"class MyClass1(list):    # subclass of list
            def fn(self):
                print 'waldo was here'
       "

Main> py"class MyClass2():     # NOT a subclass of list
            def fn(self):
                print 'waldo was here'
       "

Main> c1 = py"MyClass1()"     # misidentified as a list => Array
0-element Array{Any,1}

Main> c2 = py"MyClass2()"
PyObject <__main__.MyClass2 instance at 0x1a48492758>

Main> py"$c1.fn()"
ERROR: PyError (ccall(@pysym(:PyEval_EvalCode), PyPtr, (PyPtr, PyPtr, PyPtr), o, globals, locals)) <
type 'exceptions.AttributeError'>
AttributeError("'list' object has no attribute 'fn'",)
  File "/Users/rjp/.julia/v0.6/PyCall/src/pyeval.jl", line 1, in <module>
    const Py_single_input = 256  # from Python.h

Stacktrace:
 [1] pyerr_check at /Users/rjp/.julia/v0.6/PyCall/src/exception.jl:60 [inlined]
 [2] pyerr_check at /Users/rjp/.julia/v0.6/PyCall/src/exception.jl:64 [inlined]
 [3] macro expansion at /Users/rjp/.julia/v0.6/PyCall/src/exception.jl:84 [inlined]
 [4] pyeval_(::String, ::PyCall.PyDict{String,PyCall.PyObject,false}, ::PyCall.PyDict{String,PyCall.
PyObject,false}, ::Int64, ::String) at /Users/rjp/.julia/v0.6/PyCall/src/pyeval.jl:23
 [5] eval(::Module, ::Any) at ./boot.jl:235

Main> py"$c2.fn()"
waldo was here

conversions.jl:762 から始め、Julia 環境と Python 環境で issue の MyClass1/MyClass2 の例を再現します。PyCall が Python のリストサブクラスをどのように処理するかを追跡し、完成した変更によってサブクラスのメソッドへのアクセスが維持され、通常のリストも引き続き正しく処理されることを確認します。