pub fn show_element(&mut self, index: usize) -> Option<usize> {
		Some(
			self.show_element_upward(index)?
				+ self.show_element_downward(index)?,
		)
	}
/// makes sure `index` is visible.
/// this expands all parents and shows all siblings
makes sure `index` is visible.
this expands all parents and shows all siblings
makes sure ` index ` is visible . this expands all parents and shows all siblings
pub fn show_element(&mut self, index: usize) -> Option<usize> {
		Some(
			self.show_element_upward(index)?
				+ self.show_element_downward(index)?,
		)
	}
pub fn show_element ( & mut self , index : usize ) -> Option < usize > { Some ( self . show_element_upward ( index ) ? + self . show_element_downward ( index ) ? , ) }
makes sure `index` is visible.
makes sure ` index ` is visible .
&mut self
index
usize