The format of pem.lmdb is inconsistent between it in preprocess_all and in LookupsInferenceOnly class

[JerryZeyu]

In the LookupsInferenceOnly Class from the data_lookupss.py, the format of self.pem is Mapping[str, List[Tuple[str, float]]]. But in the preprocess_all.py, when we use it to download data and build the pem.lmdb, the format is Mapping[str, Mapping[str, float]]. So this inconsistent would result in the errors when load the data.