@classmethod
def _check_template_missing_keys(cls, dictionary):
    """Checks if the loaded template is complete.

        Parameters
        ----------
        dictionary : dict
            Template's dictionary to be evaluated

        Returns
        -------
        missing_keys : list[str]
            List of missing keys
        """
    necessary_keys = ['OPEN_HTML', 'OPEN_GENERAL', 'OPEN_GENERAL_UL',
        'GENERAL_LI', 'CLOSE_GENERAL_UL', 'CLOSE_GENERAL', 'OPEN_ITEMS',
        'OPEN_ITEMS_UL', 'ITEMS_LI', 'CLOSE_ITEMS_UL', 'CLOSE_ITEMS',
        'OPEN_HEROES', 'OPEN_HEROES_UL', 'HEROES_LI', 'CLOSE_HEROES_UL',
        'CLOSE_HEROES', 'CLOSE_HTML']
    missing_keys = []
    for item in necessary_keys:
        if item not in dictionary.keys():
            missing_keys.append(item)
    return missing_keys
