[unkn0wn]

from calibre.web.feeds.news import BasicNewsRecipe

class xyz(BasicNewsRecipe):
    title = 'tem'
    encoding = 'utf-8'
    use_embedded_content = False
    remove_javascript = True
    no_stylesheets = True
    remove_attributes = ['height', 'width', 'style']
    auto_cleanup = True

    def parse_index(self):
        return [('Tem', [{'title': 'Article', 'url': 'https://www.tematika.com/'},]),]

this is not an article.. try with auto_cleanup true, if nothing try false.