fix typos and clippy

crates/polars-parquet/src/arrow/read/deserialize/binary/basic.rs

@@ -213,7 +213,7 @@ impl<O: Offset> utils::Decoder for BinaryDecoder<O> {
 
             fn target_reserve(&self, target: &mut Self::Target, n: usize) {
                 // @NOTE: This is an estimation for the reservation. It will probably not be
-                // accurate, but then it is a lot better then not allocating.
+                // accurate, but then it is a lot better than not allocating.
                 target.offsets.reserve(n);
                 target.values.reserve(n);
             }

crates/polars-parquet/src/arrow/read/deserialize/nested_utils.rs

@@ -567,7 +567,7 @@ pub struct PageNestedDictArrayDecoder<
     _pd: std::marker::PhantomData<K>,
 }
 
-/// Return the defintion and repetition level iterators for this page.
+/// Return the definition and repetition level iterators for this page.
 fn level_iters(page: &DataPage) -> ParquetResult<(HybridRleDecoder, HybridRleDecoder)> {
     let split = split_buffer(page)?;
     let def = split.def;

crates/polars/tests/it/io/parquet/read/utils.rs

@@ -54,30 +54,6 @@ impl<'a> DefLevelsDecoder<'a> {
     }
 }
 
-/// Iterator adapter to convert an iterator of non-null values and an iterator over validity
-/// into an iterator of optional values.
-#[derive(Debug, Clone)]
-pub struct OptionalValues<T, V: Iterator<Item = bool>, I: Iterator<Item = T>> {
-    validity: V,
-    values: I,
-}
-
-impl<T, V: Iterator<Item = bool>, I: Iterator<Item = T>> Iterator for OptionalValues<T, V, I> {
-    type Item = Option<T>;
-
-    #[inline]
-    fn next(&mut self) -> Option<Self::Item> {
-        self.validity
-            .next()
-            .map(|x| if x { self.values.next() } else { None })
-    }
-
-    #[inline]
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        self.validity.size_hint()
-    }
-}
-
 pub fn deserialize_optional<C: Clone, I: Iterator<Item = ParquetResult<C>>>(
     validity: DefLevelsDecoder,
     values: I,