import re


def get_template_keys_from_string(template_string):
    """
    Retrieve all the keys from the template string which are identified by '{{ <key_name> }}'.

    :param template_string: the template in a string
    :type template_string: string
    :return: the list of the template keys corresponding to secret parameters
    :rtype: list[string]
    """

    keys = re.findall(r"{{([a-z0-9_ ]+)", template_string)
    trimmed_keys = [key.strip() for key in keys]

    return trimmed_keys