code: def is_builtin_css_function(name):
      
      name = name.replace('_', '-')
  
      if name in BUILTIN_FUNCTIONS:
          return True
  
      # Vendor-specific functions (-foo-bar) are always okay
      if name[0] == '-' and '-' in name[1:]:
          return True
  
      return False
docs: Returns whether the given `name` looks like the name of a builtin CSS
      function.
  
      Unrecognized functions not in this list produce warnings.