235         tab_descriptor = self._generate_tab_descriptor(tab)
236         self._tabs[tab_descriptor] = tab
238         return tab_descriptor
250     def get_tab_by_descriptor(self, tab_descriptor):  argument
256         return self._tabs[tab_descriptor]
260     def close_tab(self, tab_descriptor):  argument
266         if tab_descriptor not in self._tabs:
267             raise RuntimeError('There is no tab for %s' % tab_descriptor)
268         tab = self._tabs[tab_descriptor]
269         del self._tabs[tab_descriptor]
275             self, tab_descriptor, expression, timeout):  argument
282         if tab_descriptor not in self._tabs:
283             raise RuntimeError('There is no tab for %s' % tab_descriptor)
284         self._tabs[tab_descriptor].WaitForJavaScriptCondition(
288     def execute_javascript(self, tab_descriptor, statement, timeout):  argument
295         if tab_descriptor not in self._tabs:
296             raise RuntimeError('There is no tab for %s' % tab_descriptor)
297         self._tabs[tab_descriptor].ExecuteJavaScript(
301     def evaluate_javascript(self, tab_descriptor, expression, timeout):  argument
309         if tab_descriptor not in self._tabs:
310             raise RuntimeError('There is no tab for %s' % tab_descriptor)
311         return self._tabs[tab_descriptor].EvaluateJavaScript(