class Selenium::WebDriver::BiDi::Serialization::Union

def variant_for(tag, &supplied)

The matching variant's ref, or nil when none matches (the fallback if declared).
def variant_for(tag, &supplied)
  return @variants[tag] if !UNSET.equal?(tag) && @variants&.key?(tag)
  @presence&.each { |path, keys| return path if keys.all?(&supplied) }
  @fallback
end