code: def visit_Attribute(self, node):
      if node.attr.startswith("__") and node.attr.endswith("__"):
          raise ValueError("cycler strings with dunders are forbidden")
      self.generic_visit(node)
  
imports: import ast
  from functools import lru_cache, reduce
  from numbers import Real
  import operator
  import os
  import re
  import numpy
  from matplotlib import _api, cbook
  from matplotlib.cbook import ls_mapper
  from matplotlib.colors import Colormap, is_color_like
  from matplotlib._fontconfig_pattern import parse_fontconfig_pattern
  from matplotlib._enums import JoinStyle, CapStyle
  from cycler import Cycler, cycler
label_desc: Use image node_id 1 for calling the _DunderChecker obj's underlying member method code with example usage: obj.visit_Attribute(node) without return types