message: Fix 'Unhashable type' in paired t-test chart
diff: @@ -2558,7 +2558,7 @@ class PairedTTestViz(BaseViz):
  """
  fd = self.form_data
  groups = fd.get('groupby')
  - metrics = fd.get('metrics')
  + metrics = self.metric_labels
  df = df.pivot_table(
  index=DTTM_ALIAS,
  columns=groups,
  