fn sum(&self) -> Option<u32> {
        if self.is_empty() {
            return None;
        }
        let sum = self.into_iter().fold(0, |acc: u32, x| match x {
            Some(v) => acc + v as u32,
            None => acc,
        });
        Some(sum)
    }
/// Returns `None` if the array is empty or only contains null values.
Returns `None` if the array is empty or only contains null values.
Returns ` None ` if the array is empty or only contains null values .
fn sum(&self) -> Option<u32> {
        if self.is_empty() {
            return None;
        }
        let sum = self.into_iter().fold(0, |acc: u32, x| match x {
            Some(v) => acc + v as u32,
            None => acc,
        });
        Some(sum)
    }
fn sum ( & self ) -> Option < u32 > { if self . is_empty ( ) { return None ; } let sum = self . into_iter ( ) . fold ( 0 , | acc : u32 , x | match x { Some ( v ) => acc + v as u32 , None => acc , } ) ; Some ( sum ) }
Returns `None` if the array is empty or only contains null values.
Returns ` None ` if the array is empty or only contains null values .
&self
&self