def METHOD_NAME(self, pad_size, symmetric=False):
    """Add zero padding to the sample. The pad size is given in number of samples.
    If symmetric=True, `pad_size` will be added to both sides. If false, `pad_size`
    zeros will be added only to the end.
    """
    self._samples = np.METHOD_NAME(self._samples,
                           (pad_size if symmetric else 0, pad_size),
                           mode='constant')