Copy the column name list for safety.
@@ -238,7 +238,7 @@ class KgtkIdBuilder(KgtkFormat):
node1_column_idx, label_column_idx, node2_column_idx, id_column_idx = \
KgtkReader.get_special_columns(column_name_map, "", "idbuilder")
- return cls.new1(column_names, column_name_map, node1_column_idx, label_column_idx, node2_column_idx, id_column_idx, options)
+ return cls.new1(column_names.copy(), column_name_map, node1_column_idx, label_column_idx, node2_column_idx, id_column_idx, options)
@classmethod
def new1(cls,
