Remove many unwrap

src/import.rs

@@ -512,7 +512,7 @@ impl ImportState {
             .map(|name| (name.clone(), Vec::<usize>::with_capacity(1)))
             .collect::<Vec<_>>();
         for (key, endpoint) in &group.mapping {
-            let property_index = group.fields.iter().position(|f| f == key).unwrap();
+            let property_index = group.fields.iter().position(|f| f == key).expect("Unknown property");
             let group_index = result
                 .iter()
                 .position(|(name, _)| name == endpoint)