How to use the zvt.domain.StockCategory function in zvt

def get_securities_in_blocks(provider: str = 'eastmoney',
                             categories: List[Union[str, StockCategory]] = ['concept', 'industry'],
                             names=None, codes=None, ids=None):
    session = get_db_session(provider=provider, data_schema=Index)

    categories = [StockCategory(category).value for category in categories]

    filters = [Index.category.in_(categories)]

    # add name filters
    if names:
        filters.append(Index.name.in_(names))

    blocks = get_entities(entity_ids=ids, codes=codes, entity_type='index', provider=provider,
                          filters=filters, return_type='domain', session=session)
    securities = []
    for block in blocks:
        securities += [item.stock_id for item in block.stocks]

    return securities

def generate_url(self, category, code, number):
        if category == StockCategory.industry.value:
            block = 0
        elif category == StockCategory.concept.value:
            block = 1

        return self.url.format(number, block, code)

def get_indices(provider: str = 'sina',
                block_category: Union[str, StockCategory] = 'concept',
                return_type: str = 'df') -> object:
    """
    get indices/blocks on block_category

    :param provider:
    :type provider:
    :param block_category:
    :type block_category:
    :param return_type:
    :type return_type:
    :return:
    :rtype:
    """
    if type(block_category) == StockCategory:
        block_category = block_category.value

    session = get_db_session(provider=provider, data_schema=Index)

    filters = [Index.category == block_category]
    blocks = get_entities(entity_type='index', provider=provider, filters=filters,
                          session=session, return_type=return_type)
    return blocks