code: def from_pygments_lexer_cls(cls, lexer_cls):
          
          patterns = {
              # For Python, start highlighting at any class/def block.
              'Python':   r'^\s*(class|def)\s+',
              'Python 3': r'^\s*(class|def)\s+',
  
              # For HTML, start at any open/close tag definition.
              'HTML': r'<[/a-zA-Z]',
  
              # For javascript, start at a function.
              'JavaScript': r'\bfunction\b'
  
              # TODO: Add definitions for other languages.
              #       By default, we start at every possible line.
          }
          p = patterns.get(lexer_cls.name, '^')
          return cls(p)
docs: Create a :class:`.RegexSync` instance for this Pygments lexer class.