code: def astype(self, np_type):
          
          return Signal(
              self.samples.astype(np_type),
              self.timestamps,
              unit=self.unit,
              name=self.name,
              conversion=self.conversion,
              raw=self.raw,
              master_metadata=self.master_metadata,
              display_name=self.display_name,
              attachment=self.attachment,
              stream_sync=self.stream_sync,
              invalidation_bits=self.invalidation_bits,
              source=self.source,
              encoding=self.encoding,
          )
docs: returns new *Signal* with samples of dtype *np_type*
  
          Parameters
          ----------
          np_type : np.dtype
              new numpy dtye
  
          Returns
          -------
          signal : Signal
              new *Signal* with the samples of *np_type* dtype