docs: def single_valued(self, e):
          """
          Returns True whether `e` is a concrete value or is a value set with
          only 1 possible value. This differs from `unique` in that this *does*
          not query the constraint solver.
          """
          if self.state.mode == 'static':
              if type(e) in (int, bytes, float, bool):
                  return True
              else:
                  return e.cardinality <= 1
  
          else:
              # All symbolic expressions are not single-valued
              return not self.symbolic(e)