Formatting and dart analyze fixes

example/lib/main.dart

@@ -68,7 +68,7 @@ class _MyHomePageState extends State<MyHomePage> {
         child: Column(
           mainAxisAlignment: MainAxisAlignment.center,
           children: <Widget>[
-            Text(
+            const Text(
               'Enter your card details below:',
             ),
             CardTextField(

lib/card_details.dart

@@ -37,7 +37,6 @@ class CardDetails {
   int _lastCheckHash = 0;
   CardProvider? provider;
 
-
   /// Checks the validity of the `CardDetails` and returns the result.
   ValidState get validState {
     checkIsValid();
@@ -269,7 +268,7 @@ enum CardProviderID {
 class CardProvider {
   CardProviderID id;
   List<int>? innValidNums;
-  List<_Range>? innValidRanges;
+  List<Range>? innValidRanges;
   int cardLength;
   int cvcLength;
 
@@ -290,11 +289,11 @@ class CardProvider {
 /// Object for `CardProvider` to determine valid number ranges.
 /// A loose wrapper on a tuple, that provides assertion of
 /// valid inputs and the `isWithin()` helper function.
-class _Range {
+class Range {
   int high;
   int low;
 
-  _Range({required this.low, required this.high}) {
+  Range({required this.low, required this.high}) {
     assert(low <= high);
   }
 
@@ -328,7 +327,7 @@ List<CardProvider> _providers = [
     cardLength: 16,
     cvcLength: 3,
     innValidNums: [60, 65],
-    innValidRanges: [_Range(low: 644, high: 649)],
+    innValidRanges: [Range(low: 644, high: 649)],
   ),
   CardProvider(
     id: CardProviderID.jcb,
@@ -340,7 +339,7 @@ List<CardProvider> _providers = [
     id: CardProviderID.mastercard,
     cardLength: 16,
     cvcLength: 3,
-    innValidRanges: [_Range(low: 22, high: 27), _Range(low: 51, high: 55)],
+    innValidRanges: [Range(low: 22, high: 27), Range(low: 51, high: 55)],
   ),
   CardProvider(
     id: CardProviderID.visa,

lib/stripe_native_card_field.dart

@@ -33,6 +33,7 @@ class CardTextField extends StatefulWidget {
   final BoxDecoration? boxDecoration; // TODO unapplied style
   final BoxDecoration? errorBoxDecoration; // TODO unapplied style
   final double width;
+
   /// Callback that returns the completed CardDetails object
   final void Function(CardDetails) onCardDetailsComplete;
   final double? height;