code: def create_new_version(
          self,
          name,
          subject,
          text='',
          template_id=None,
          html=None,
          locale=None,
          timeout=None
      ):
          
          if(html):
              payload = {
                  'name': name,
                  'subject': subject,
                  'html': html,
                  'text': text
              }
          else:
              payload = {
                  'name': name,
                  'subject': subject,
                  'text': text
              }
  
          if locale:
              url = self.TEMPLATES_SPECIFIC_LOCALE_VERSIONS_ENDPOINT % (
                  template_id,
                  locale
              )
          else:
              url = self.TEMPLATES_NEW_VERSION_ENDPOINT % template_id
  
          return self._api_request(
              url,
              self.HTTP_POST,
              payload=payload,
              timeout=timeout
          )
docs: API call to create a new version of a template