'add_featurewise_stdnorm.
Scale each sample by the specified standard deviation. If no std
specified, std is evaluated over all samples data.
Arguments:
std: `float` (optional). Provides a custom standard derivation.
If none provided, it will be automatically caluclated based on
the training dataset. Default: None.
Returns:
Nothing.'

def add_featurewise_stdnorm(self, std=None):

    self.global_std.is_required = True
    self.global_std.value = std
    self.methods.append(self._featurewise_stdnorm)
    self.args.append(None)
