code: def df_metrics_to_num(self, df, query_object):
          
          metrics = [metric for metric in query_object.metrics]
          for col, dtype in df.dtypes.items():
              if dtype.type == np.object_ and col in metrics:
                  df[col] = pd.to_numeric(df[col], errors='coerce')
docs: Converting metrics to numeric when pandas.read_sql cannot