class_docstr: A callable for converting CSS declarations to ExcelWriter styles
  
  Supports parts of CSS 2.2, with minimal CSS 3.0 support (e.g. text-shadow),
  focusing on font styling, backgrounds, borders and alignment.
  
  Operates by first computing CSS styles in a fairly generic
  way (see :meth:`compute_css`) then determining Excel style
  properties from CSS properties (see :meth:`build_xlstyle`).
  
  Parameters
  ----------
  inherited : str, optional
      CSS declarations understood to be the containing scope for the
      CSS processed by :meth:`__call__`.
code: def color_to_excel(self, val):
      if val is None:
          return None
      if val.startswith("#") and len(val) == 7:
          return val[1:].upper()
      if val.startswith("#") and len(val) == 4:
          return (val[1] * 2 + val[2] * 2 + val[3] * 2).upper()
      try:
          return self.NAMED_COLORS[val]
      except KeyError:
          warnings.warn(
              "Unhandled color format: {val!r}".format(val=val),
              CSSWarning,
          )
  
imports: import itertools
  import re
  import warnings
  import numpy
  from pandas.compat import reduce
  from pandas.core.dtypes import missing
  from pandas.core.dtypes.common import is_float, is_scalar
  from pandas.core.dtypes.generic import ABCMultiIndex, ABCPeriodIndex
  from pandas import Index
  import pandas.core.common
  from pandas.io.formats.css import CSSResolver, CSSWarning
  from pandas.io.formats.format import get_level_lengths
  from pandas.io.formats.printing import pprint_thing
label_desc: Use image node_id 9 for calling the CSSToExcelConverter obj's underlying member method code with example usage: obj.color_to_excel(val) and returns: None, val, unknown, self