code: def SideEffect(self, side_effect, target):
          
          side_effects = self.arg2nodes(side_effect, self.fs.Entry)
          targets = self.arg2nodes(target, self.fs.Entry)
  
          for side_effect in side_effects:
              if side_effect.multiple_side_effect_has_builder():
                  raise SCons.Errors.UserError("Multiple ways to build the same target were specified for: %s" % str(side_effect))
              side_effect.add_source(targets)
              side_effect.side_effect = 1
              self.Precious(side_effect)
              for target in targets:
                  target.side_effects.append(side_effect)
          return side_effects
docs: Tell scons that side_effects are built as side
          effects of building targets.