code: function isTokenSeparated(stream) {
          return stream.sol() ||
              stream.string.charAt(stream.start - 1) == " " ||
              stream.string.charAt(stream.start - 1) == "\t";
      }
docs: return true if the current token is seperated from the tokens before it which means either this is the start of the line, or there is at least one space or tab character behind the token otherwise returns false