'add_samplewise_zero_center.
Zero center each sample by subtracting it by its mean.
Arguments:
per_channel: `bool`. If True, apply per channel mean.
Returns:
Nothing.'

def add_samplewise_zero_center(self, per_channel=False):

    self.methods.append(self._samplewise_zero_center)
    self.args.append([per_channel])
