How to change the selection shape of calendar’s date cell selection?

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
xmlns:LocalNamespace="clr-namespace:GettingStartedKBSyncfusion"
xmlns:Syncfusion ="clr-namespace:Syncfusion.SfCalendar.XForms;assembly=Syncfusion.SfCalendar.XForms"
x:Class="GettingStartedKBSyncfusion.MainPage">
<ContentPage.Content>
<Syncfusion:SfCalendar x:Name="calendar">
    <Syncfusion:SfCalendar.MonthViewSettings>
        <Syncfusion:MonthViewSettings SelectionShape="Circle"/>
    </Syncfusion:SfCalendar.MonthViewSettings>
</Syncfusion:SfCalendar>
</ContentPage.Content>
</ContentPage>