'Utility function for displaying layer info with a given indentation level.
Arguments:
level (int, optional): indentation level
Returns:
str: layer info at the given indentation level'

def nested_str(self, level=0):

    ss = (self.classnm + '\n')
    ss += '\n'.join([l.nested_str((level + 1)) for l in self.layers])
    return ss
