code: def validate_sketch(s):
      if isinstance(s, str):
          s = s.lower().strip()
          if s.startswith("(") and s.endswith(")"):
              s = s[1:-1]
      if s == "none" or s is None:
          return None
      try:
          return tuple(_listify_validator(validate_float, n=3)(s))
      except ValueError as exc:
          raise ValueError(
              "Expected a (scale, length, randomness) tuple"
          ) from exc
  
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 32 for calling a global function with example usage: validate_sketch(s) and returns: None, tuple