filter() expects you to use the raw PostgREST syntax for the filter values.
supabase.postgrest["characters"].select \{
filter(column = "name", operator = FilterOperator.IN, value = "('Han', 'Katniss')")
\}
supabase.postgrest["orchestral_sections"].select(
columns = Columns.raw("""
name,
instruments!inner (
name
)
""")
) \{
filter(column = "instruments.name", operator = FilterOperator.EQ, value = "flute")
\}