Not able to call C++ API with numpy array of user defined structs

[rajnishdahiya]

I have went through documentation and searched a lot on internet but couldn't find any resolution. Here is relevant code snippet

struct Ohlc {
    double open, high, low, close;
    int volume;
};

using array_dtype = Ohlc;

void calculate_ema_pyarray(const py::array_t<const array_dtype,
     py::array::c_style | py::array::forcecast> array) {
 // DO something with array
}

PYBIND11_MODULE(ema_calculator_pybind11, m) {
  // optional module docstring
  m.doc() = "pybind11 plugin for ema calculations";

  py::class_<Ohlc>(m, "Ohlc")
      .def(py::init<>())
      .def_readwrite("open", &Ohlc::open)
      .def_readwrite("high", &Ohlc::high)
      .def_readwrite("low", &Ohlc::low)
      .def_readwrite("close", &Ohlc::close);

     PYBIND11_NUMPY_DTYPE(Ohlc, open, high, low, close);

  m.def("calculate_ema", &calculate_ema_pyarray,
     "Calculates EMA for given input");
}

Below is the error I get while using it in python

>>> from ema_calculator_pybind11 import *
>>> import numpy as np
>>> calculate_ema(np.array([Ohlc()]))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: calculate_ema(): incompatible function arguments. The following argument types are supported:
    1. (arg0: numpy.ndarray[ema_calculator_pybind11.Ohlc]) -> None

Invoked with: array([<ema_calculator_pybind11.Ohlc object at 0x7f926d284670>],
      dtype=object)

Above works if I change array_dtype to build-in type, e.g. using array_dtype = double; or if I take only 1 object of Ohlc instead of an array.
Not sure if it's a missing feature or bug or quite likely something missing in my code. Please advise.