245         tab_descriptor = self._generate_tab_descriptor(tab)
246         self._tabs[tab_descriptor] = tab
248         return tab_descriptor
282     def get_tab_by_descriptor(self, tab_descriptor):  argument
288         return self._tabs[tab_descriptor]
292     def close_tab(self, tab_descriptor):  argument
298         if tab_descriptor not in self._tabs:
299             raise RuntimeError('There is no tab for %s' % tab_descriptor)
300         tab = self._tabs[tab_descriptor]
301         del self._tabs[tab_descriptor]
307             self, tab_descriptor, expression, timeout):  argument
314         if tab_descriptor not in self._tabs:
315             raise RuntimeError('There is no tab for %s' % tab_descriptor)
316         self._tabs[tab_descriptor].WaitForJavaScriptCondition(
320     def execute_javascript(self, tab_descriptor, statement, timeout):  argument
327         if tab_descriptor not in self._tabs:
328             raise RuntimeError('There is no tab for %s' % tab_descriptor)
329         self._tabs[tab_descriptor].ExecuteJavaScript(
333     def evaluate_javascript(self, tab_descriptor, expression, timeout):  argument
341         if tab_descriptor not in self._tabs:
342             raise RuntimeError('There is no tab for %s' % tab_descriptor)
343         return self._tabs[tab_descriptor].EvaluateJavaScript(