code: def switch_application(self, index_or_alias):
          
          old_index = self._cache.current_index
          if index_or_alias is None:
              self._cache.close()
          else:
              self._cache.switch(index_or_alias)
          return old_index
docs: Switches the active application by index or alias.
  
          `index_or_alias` is either application index (an integer) or alias
          (a string). Index is got as the return value of `Open Application`.
  
          This keyword returns the index of the previous active application,
          which can be used to switch back to that application later.
  
          Example:
          | ${appium1}=              | Open Application  | http://localhost:4723/wd/hub                   | alias=MyApp1 | platformName=iOS | platformVersion=7.0 | deviceName='iPhone Simulator' | app=your.app |
          | ${appium2}=              | Open Application  | http://localhost:4755/wd/hub                   | alias=MyApp2 | platformName=iOS | platformVersion=7.0 | deviceName='iPhone Simulator' | app=your.app |
          | Click Element            | sendHello         | # Executed on appium running at localhost:4755 |
          | Switch Application       | ${appium1}        | # Switch using index                           |
          | Click Element            | ackHello          | # Executed on appium running at localhost:4723 |
          | Switch Application       | MyApp2            | # Switch using alias                           |
          | Page Should Contain Text | ackHello Received | # Executed on appium running at localhost:4755 |