class_docstr: Set default foreground/background color for output that doesn't specify
  anything. This is useful for overriding the terminal default colors.
  
  :param fg: Color string or callable that returns a color string for the
      foreground.
  :param bg: Like `fg`, but for the background.
class_docstr_tok: ["Set","default","foreground\/background","color","for","output","that","does","n't","specify","anything",".","This","is","useful","for","overriding","the","terminal","default","colors",".",":","param","fg",":","Color","string","or","callable","that","returns","a","color","string","for","the","foreground",".",":","param","bg",":","Like","`","fg","`",",","but","for","the","background","."]
code: def transform_attrs(self, attrs: Attrs) -> Attrs:
      if attrs.bgcolor in ("", "default"):
          attrs = attrs._replace(bgcolor=parse_color(to_str(self.bg)))
  
      if attrs.color in ("", "default"):
          attrs = attrs._replace(color=parse_color(to_str(self.fg)))
  
      return attrs
  
imports: from __future__ import annotations
  from abc import ABCMeta, abstractmethod
  from colorsys import hls_to_rgb, rgb_to_hls
  from typing import Callable, Hashable, Sequence
  from prompt_toolkit.cache import memoized
  from prompt_toolkit.filters import FilterOrBool, to_filter
  from prompt_toolkit.utils import AnyFloat, to_float, to_str
  from .base import ANSI_COLOR_NAMES, Attrs
  from .style import parse_color
label_desc: Use image node_id 2 for calling the SetDefaultColorStyleTransformation obj's underlying member method code with example usage: obj.transform_attrs(attrs) and returns: attrs