code: def get_stdev(self, asset_type):
          
          load_times = []
          # Handle edge cases like TTFB
          if asset_type == 'ttfb':
              for page in self.pages:
                  if page.time_to_first_byte is not None:
                      load_times.append(page.time_to_first_byte)
          elif asset_type not in self.asset_types and asset_type != 'page':
              raise ValueError('asset_type must be one of:\nttfb\n{0}'.format(
                      '\n'.join(self.asset_types)))
          else:
              load_times = self.get_load_times(asset_type)
  
          if not load_times or not sum(load_times):
              return 0
          return round(stdev(load_times),
                       self.decimal_precision)
docs: Returns the standard deviation for a set of a certain asset type.
  
          :param asset_type: ``str`` of the asset type to calculate standard
          deviation for.
          :returns: A ``int`` or ``float`` of standard deviation, depending on
          the self.decimal_precision