code: def parse(self, xsl='text'):
          
  
          try:
              cmd_text, option_text = xsl.split(None, 1)
          except ValueError:
              cmd_text = xsl
              option_text = ''
  
          try:
              context, cmd = cmd_text.strip().lower().split(':', 1)
          except ValueError:
              cmd = cmd_text.lower()
              context = None
  
          if not cmd in DEFAULT_CMD_TO_CONTEXT_MAPPING:
              raise ParseError("unknown command %s" % cmd)
  
          if context and not context in CONTEXTS:
              raise ParseError("unknown context %s" % context)
  
          self.context = context
          self.cmd = cmd
          self.text = None
          self.meta_commands = []
          self.options = {}
  
          try:
              if cmd in ('choose', 'text', 'meta'):
                  raise ValueError()
              option_name, expr = option_text.split('=', 1)
              option_name = option_name.strip().lower()
              expr = unescape(expr).strip("'").strip('"').strip()
              self.options = {option_name: expr}
  
          except ValueError:
              text = unescape(option_text)
  
              if cmd == 'meta':
                  for mc in filter(lambda c: c, map(lambda c: c.strip(), text.lower().split(';'))):
                      if mc in META_COMMANDS:
                          # store in stack order
                          self.meta_commands = [mc] + self.meta_commands
                      else:
                          raise ParseError("unknown meta command %s" % self.text)
  
              else:
                  self.text = text
docs: TODO: add double-quoted string literals that allows for escaped double quotes
          https://gist.github.com/prathe/2439752 or
          http://www.metaltoad.com/blog/regex-quoted-string-escapable-quotes