How to set default choiceType in symfony or twig

I am trying to get default radio checked with symfony or twig but i am not able to do

for example i have a gender form field that contains male and female and i want to have one of them to be checked by default

i looked in symfony documentation but i din't find any solution

This is the formfield that i want to set a default

->add('gender', ChoiceType::class, [
      'choices' => [
           'Male' => 'male',
           'Female' => 'female',
       ],
       'expanded' => true
])

This is twig code

{% for gender in form.member.gender %}
  {{
       form_row(gender, {label_attr: {'class': 'radio-custom'}})
  }}
{% endfor %}