title: The argument type 'List<Set<Card>>' can't be assigned to the parameter type 'List<Widget>'
body: <p>Flutter shows me the following error message although I converted <code>map</code> into <code>List</code></p>
  <pre><code>The argument type 'List&lt;Set&lt;Card&gt;&gt;' can't be assigned to the parameter type 'List&lt;Widget&gt;'.dartargument_type_not_assignable
  </code></pre>
  <p>May you please tell me what's wrong?</p>
  <pre class="lang-dart prettyprint-override"><code>class MyHomePage extends StatelessWidget {
    MyHomePage({Key? key, required String title}) : super(key: key);
  
    final List&lt;Transaction&gt; transactions = [
      Transaction(
          id: 'sh1', 
          date: DateTime.now(), 
          title: 'School', 
          value: 1554.5
          ),
      Transaction(
        id: 'sc5',
        date: DateTime.now(), 
        title: 'Sucar', 
        value: 16.5
        ),
    ];
  
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text(&quot;title&quot;),
        ),
        body: Column(
          crossAxisAlignment: CrossAxisAlignment.stretch,
          children: [
            const Card(
              color: Color.fromRGBO(200, 165, 245, 1.0),
              child: Text('[CHART]'),
            ),
            Column(
              children:
  /////// ERROR
                transactions.map( (e) =&gt; { return Card(child: Text(e.title),); } ).toList(),
            ),
          ],
        ),
      );
    }
  }
  </code></pre>