code: def get_cache_key(self, name, filename=None):
          
          hash = sha1(name.encode('utf-8'))
          if filename is not None:
              filename = '|' + filename
              if isinstance(filename, text_type):
                  filename = filename.encode('utf-8')
              hash.update(filename)
          return hash.hexdigest()
docs: Returns the unique hash key for this template name.