from six import iteritems

def get_all_keys(dictionary, result_list=[]):
    """
        Method to get all keys from a nested dictionary as a List

        Args:
            dictionary: Nested dictionary

        Returns:
            List of keys in the dictionary
    """
    for key, value in iteritems(dictionary):
        if isinstance(value, dict):
            result_list.append(key)
            get_all_keys(dictionary=value, result_list=result_list)
        else:
            result_list.append(key)
    return result_list


details = {
    "hardware_details": {
        "model_name": "MacBook Pro",
        "processor_details": {
            "processor_name": "Intel Core i7",
            "processor_speed": "2.7 GHz",
            "core_details": {
                "total_numberof_cores": "4",
                "l2_cache(per_core)": "256 KB"
            }
        },
        "total_number_of_cores": "4",
        "memory": "16 GB",
    },
    "os_details": {
        "product_version": "10.13.6",
        "build_version": "17G65"
    },
    "name": "Test",
    "date": "YYYY-MM-DD HH:MM:SS"
}

print get_all_keys(dictionary=details)