check the typing signatures

[pnrobinson]

In HPOStatisticsAnalyzer, we have this function

  def compute_correlation_matrix(
            self, 
            correlation_type: CorrelationType = CorrelationType.SPEARMAN, 
            n_jobs: int = -1,
        ) -> None:

But it actually returns a pd.DataFrame. The code still works, but it is marked as an error. For instance

df = df[(df["p_value_corrected"]<0.05) & (df["correlation"] > 0.5)]

In my system, df is marked with a red error that says Object of type "None" is not subscriptablePylance

This is because according to the typing annotations, the function seems to be returning None.
We should try to make sure that the code shows no errors like this!