'add_random_blur.
Randomly blur an image by applying a gaussian filter with a random
sigma (0., sigma_max).
Arguments:
sigma: `float` or list of `float`. Standard deviation for Gaussian
kernel. The standard deviations of the Gaussian filter are
given for each axis as a sequence, or as a single number,
in which case it is equal for all axes.
Returns:
Nothing.'

def add_random_blur(self, sigma_max=5.0):

    self.methods.append(self._random_blur)
    self.args.append([sigma_max])
