Fix overhead allocation tests, clean up some imports

src/graph/sql_rule.rs

@@ -3,8 +3,7 @@ use std::fs::File;
 use super::node::RunnableNode;
 use crate::io::{DataSource, SourceType};
 use async_trait::async_trait;
-use polars::io::SerReader;
-use polars::prelude::{IntoLazy, LazyFrame, ParquetReader, ScanArgsParquet};
+use polars::prelude::{LazyFrame, ScanArgsParquet};
 use polars::{
     io::SerWriter,
     prelude::{CsvWriter, LazyCsvReader, LazyFileListReader},