Bug - Incorrect variable name in Trace.load_traces() method

[fengxizhou]

The local variable trace_df should be df in the load_traces() method.

HolisticTraceAnalysis/hta/common/trace.py

Line 464 in 2b8a33d

for rank, trace_df in self.traces.items():

The correct code should be:

for rank, df in self.traces.items():
            df = self.traces[rank].set_index("index", drop=False)
            df.index.names = [None]
            self.traces[rank] = df