input: Write a python function to create a subclass of BaseClass that implements method1 to set var1. 
  assert isinstance(SubClass(), BaseClass)
  assert hasattr(SubClass(), 'method1')
  obj = SubClass()
  obj.method1(10)
  assert obj.var1 == 10
output: class SubClass(BaseClass):
      def method1(self, value):
          self.var1 = value