code: def represent_datetime(self, d):
          
  
          fixed_format = self.get('timestamp_format')
          if fixed_format:
              rep = string_decode(d.strftime(fixed_format), 'UTF-8')
          else:
              format_hook = self.get_hook('timestamp_format')
              if format_hook:
                  rep = string_decode(format_hook(d), 'UTF-8')
              else:
                  rep = pretty_datetime(d)
          return rep
docs: turns a given datetime obj into a string representation.
          This will:
  
          1) look if a fixed 'timestamp_format' is given in the config
          2) check if a 'timestamp_format' hook is defined
          3) use :func:`~alot.helper.pretty_datetime` as fallback