docs: def to_tuple(self):
          '''Convert the source sequence to a tuple.
  
          Note: This method uses immediate execution.
          '''
          if self.closed():
              raise ValueError("Attempt to call to_tuple() on a closed Queryable.")
  
          if isinstance(self._iterable, tuple):
              return self._iterable
          tup = tuple(self)
          # Ideally we would close here
          #self.close()
          return tup