code: def ifelse(self, node):
          'ifelse = "if" expr "then" expr "else" expr'
          _, cond, _, cons, _, alt = node
          return self.eval(cons) if self.eval(cond) else self.eval(altf ifelse(self, node):
          'ifelse = "if" expr "then" expr "else" expr'
          _, cond, _, cons, _, alt = node
          return self.eval(cons) if self.eval(cond) else self.eval(alt)
docs: ifelse = "if" expr "then" expr "else" expr