code: def add(self, **kwargs):
          
          for name, var in kwargs.items():
              if iskeyword(name):
                  var['name'] = name
                  name = '_' + name
              if name in self:
                  self[name] = merge(self[name], Variable(self.default_type, **var))
              else:
                  self[name] = Variable(self.default_type, **var)
          return self
docs: Add additional single Variable objects to the Variables
          object.