code: def get_template_name(self, template_name):
          
          if template_name is None:
              # Build default template path.
              template_name = self.default_form_template
          if '.html' not in template_name:  # Shortcut, e.g.: .
              template_name = '%s%s.html' % ('sitegate/%s/', template_name)
          if '%s' in template_name:  # Fill in the flow type placeholder.
              template_name = template_name % self.flow_type
          return template_name
docs: Returns template path, either from a shortcut built-in template
          name (`form_as_p`) or a template path (`my_sitegate/my_tpl.html`).
  
          Note that template path can include one `%s` placeholder. In that case
          it will be replaced with flow type (`signin` or `signup`).