'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):

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