bug: ibis.pivot_wider fails when names_from is not string #11615

df = pl.DataFrame([{'series': 0,
  'day': 0,
  'pos': 7,
  'neg': 17},
 {'series': 0,
  'day': 3,
  'pos': 34,
  'neg': 17}])

tbl = ibis.memtable(df)
wtbl = tbl.pivot_wider(
    names_from="day",
    id_cols=["series", "pos", "neg"],
    values_from=["pos", "neg"],
    values_fill=0,
    names_sort=True,
    names_sep=":",
)

  File ibis/expr/types/relations.py:4461 in pivot_wider
    id_cols: s.Selector | None = None,

TypeError: sequence item 1: expected str instance, int found