fn next(&mut self) -> Option<Self::Item> {
        match self.current {
            x if x < self.keys.len() => {
                self.current += 1;
                self.collection
                    .groups
                    .get_key_value(self.keys[self.current - 1])
            }
            _ => None,
        }
    }
/// Returns the next group, if any.
Returns the next group, if any.
Returns the next group if any .
fn next(&mut self) -> Option<Self::Item> {
        match self.current {
            x if x < self.keys.len() => {
                self.current += 1;
                self.collection
                    .groups
                    .get_key_value(self.keys[self.current - 1])
            }
            _ => None,
        }
    }
fn next ( & mut self ) -> Option < Self :: Item > { match self . current { x if x < self . keys . len ( ) => { self . current += 1 ; self . collection . groups . get_key_value ( self . keys [ self . current - 1 ] ) } _ => None , } }
Returns the next group, if any.
Returns the next group if any .
&mut self
&mut self