code: def convert(self, value, param, ctx):
          
          value = super(PositiveInt, self).convert(value, param, ctx)
          if value < 0:
              self.fail('%s is not positive' % value, param, ctx)
          if not self.allow_zero and not value:
              self.fail('%s is not greater than 0' % value, param, ctx)
          return value
docs: Reuse standard integer validator but add checks on sign and zero.