code: def push(self, vs):
          'Move given sheet `vs` to index 0 of list `sheets`.'
          if vs:
              vs.vd = self
              if vs in self.sheets:
                  self.sheets.remove(vs)
                  self.sheets.insert(0, vs)
              elif not vs.loaded:
                  self.sheets.insert(0, vs)
                  vs.reload()
                  vs.recalc()  # set up Columns
              else:
                  self.sheets.insert(0, vs)
  
              if vs.precious and vs not in vs.vd.allSheets:
                  vs.vd.allSheets[vs] = vs.name
              return vf push(self, vs):
          'Move given sheet `vs` to index 0 of list `sheets`.'
          if vs:
              vs.vd = self
              if vs in self.sheets:
                  self.sheets.remove(vs)
                  self.sheets.insert(0, vs)
              elif not vs.loaded:
                  self.sheets.insert(0, vs)
                  vs.reload()
                  vs.recalc()  # set up Columns
              else:
                  self.sheets.insert(0, vs)
  
              if vs.precious and vs not in vs.vd.allSheets:
                  vs.vd.allSheets[vs] = vs.name
              return vs
docs: Move given sheet `vs` to index 0 of list `sheets`.