code: def get_content_type(self):
          
          extension = self.path_params.get('_extension')
          for ext, mime in self.EXTENSION_MAP:
              if ext == extension:
                  return mime
          # Else: use the Accept headers
          if self.response.vary is None:
              self.response.vary = ['Accept']
          else:
              self.response.vary.append('Accept')
          types = [mime for ext, mime in self.EXTENSION_MAP]
          ct = self.request.accept.best_match(types)
          # No best match found. The specification allows us to either return a
          # 406 or just use another format in this case.
          # We pick the default format, though that may become a configurable
          # behavior in the future.
          if not ct:
              ct = types[0]
          return ct
docs: Returns the Content Type to serve from either the extension or the
          Accept headers. Uses the :attr:`EXTENSION_MAP` list for all the
          configured MIME types.