code: def change_setting(self, instance_name, key, raw_value):
          
          ii = self.insts[instance_name]
          mo = self.modules[ii.module]
          if key in mo.deps:
              if raw_value not in self.insts:
                  raise ValueError("No such instance %s" % raw_value)
              vii = self.insts[raw_value]
              vmo = self.modules[vii.module]
              if not (mo.deps[key].type in vmo.inherits or
                      mo.deps[key].type == vii.module):
                  raise ValueError("%s isn't a %s" % (
                      raw_value, mo.deps[key].type))
              value = vii.object
          elif key in mo.vsettings:
              value = self.valueTypes[mo.vsettings[key].type](
                  raw_value)
          else:
              raise ValueError("No such settings %s" % key)
          self.l.info("Changing %s.%s to %s" % (instance_name,
                                                key,
                                                raw_value))
          ii.settings[key] = value
          ii.object.change_setting(key, value)
docs: Change the settings <key> to <raw_value> of an instance
              named <instance_name>.  <raw_value> should be a string and
              is properly converted.