code: def find_lexer_class_by_name(_alias):
      
      if not _alias:
          raise ClassNotFound('no lexer for alias %r found' % _alias)
      # lookup builtin lexers
      for module_name, name, aliases, _, _ in itervalues(LEXERS):
          if _alias.lower() in aliases:
              if name not in _lexer_cache:
                  _load_lexers(module_name)
              return _lexer_cache[name]
      # continue with lexers from setuptools entrypoints
      for cls in find_plugin_lexers():
          if _alias.lower() in cls.aliases:
              return cls
      raise ClassNotFound('no lexer for alias %r found' % _alias)
docs: Lookup a lexer class by alias.
  
      Like `get_lexer_by_name`, but does not instantiate the class.
  
      .. versionadded:: 2.2