def getService(self, serviceIdentifier):
if serviceIdentifier in self._services:<EOL><INDENT>return self._services[serviceIdentifier]<EOL><DEDENT>else:<EOL><INDENT>message = "<STR_LIT>""<STR_LIT>".format(serviceIdentifier)<EOL>raise Exception(message)<EOL><DEDENT>
Return the requested service instance.

:param serviceIdentifier: <str> service identifier
:return: <object> service instance