fix syntax error from previous
@@ -538,7 +538,7 @@ class VizierClass(BaseQuery):
columns = self.columns + columns
# filter columns to _unique_ columns, preserving order in python >3.6
# note that "set" does not preserve order, but dict.keys does
- columns = list(dict(columns).keys())
+ columns = list(dict.fromkeys(columns, ).keys())
# special keywords need to be treated separately
# keyword names that can mean 'all'
