Standardized method of creating a Netmiko connection using napalm attributes.

def _netmiko_open(self, device_type, netmiko_optional_args=None):
        """Standardized method of creating a Netmiko connection using napalm attributes."""
        if netmiko_optional_args is None:
            netmiko_optional_args = {}
        try:
            self._netmiko_device = ConnectHandler(
                device_type=device_type,
                host=self.hostname,
                username=self.username,
                password=self.password,
                timeout=self.timeout,
                **netmiko_optional_args
            )
        except NetMikoTimeoutException:
            raise ConnectionException("Cannot connect to {}".format(self.hostname))

        # ensure in enable mode
        self._netmiko_device.enable()
        return self._netmiko_device