Convert from onnx operator to mxnet operator.
        The converter must specify conversions explicitly for incompatible name, and
        apply handlers to operator attributes.

        Parameters
        ----------
        :param node_name : str
            name of the node to be translated.
        :param op_name : str
            Operator name, such as Convolution, FullyConnected
        :param attrs : dict
            Dict of operator attributes
        :param inputs: list
            list of inputs to the operator
        Returns
        -------
        :return mxnet_sym
            Converted mxnet symbol

def _convert_operator(self, node_name, op_name, attrs, inputs):
        """Convert from onnx operator to mxnet operator.
        The converter must specify conversions explicitly for incompatible name, and
        apply handlers to operator attributes.

        Parameters
        ----------
        :param node_name : str
            name of the node to be translated.
        :param op_name : str
            Operator name, such as Convolution, FullyConnected
        :param attrs : dict
            Dict of operator attributes
        :param inputs: list
            list of inputs to the operator
        Returns
        -------
        :return mxnet_sym
            Converted mxnet symbol
        """
        if op_name in convert_map:
            op_name, new_attrs, inputs = convert_map[op_name](attrs, inputs, self)
        else:
            raise NotImplementedError("Operator {} not implemented.".format(op_name))
        if isinstance(op_name, string_types):
            new_op = getattr(symbol, op_name, None)
            if not new_op:
                raise RuntimeError("Unable to map op_name {} to sym".format(op_name))
            if node_name is None:
                mxnet_sym = new_op(*inputs, **new_attrs)
            else:
                mxnet_sym = new_op(name=node_name, *inputs, **new_attrs)
            return mxnet_sym
        return op_name