code: def join(self, pad=None, gap=None):
          
          if not self:
              return self.EntryClass(numpy.empty((0,) * self.EntryClass._ndim))
          self.sort(key=lambda t: t.epoch.gps)
          out = self[0].copy()
          for series in self[1:]:
              out.append(series, gap=gap, pad=pad)
          return out
docs: Concatenate all of the elements of this list into a single object
  
          Parameters
          ----------
          pad : `float`, optional, default: `0.0`
              value with which to pad gaps
  
          gap : `str`, optional, default: `'raise'`
              what to do if there are gaps in the data, one of
  
              - ``'raise'`` - raise a `ValueError`
              - ``'ignore'`` - remove gap and join data
              - ``'pad'`` - pad gap with zeros
  
              If `pad` is given and is not `None`, the default is ``'pad'``,
              otherwise ``'raise'``.
  
          Returns
          -------
          series : `gwpy.types.TimeSeriesBase` subclass
               a single series containing all data from each entry in this list
  
          See Also
          --------
          TimeSeries.append
              for details on how the individual series are concatenated together