Function take_or_else

pub fn take_or_else<T: Codec + Sized, F: FnOnce() -> T>(
    child_info: &ChildInfo,
    key: &[u8],
    default_value: F,
) -> T

Return the value of the item in storage under key, or default_value() if there is no explicit entry. Ensure there is no explicit entry on return.