input: Write a python function to create a class `Shape` with methods to get and set the type and area of the shape.
  assert shape.get_type() == 'Square'
  assert shape.get_area() == 10
  shape.set_area(20)
  assert shape.get_area() == 20
output: class Shape:
      def __init__(self, shape_type, area):
          self._type = shape_type
          self._area = area
  
      def get_type(self):
          return self._type
  
      def get_area(self):
          return self._area
  
      def set_area(self, new_area):
          self._area = new_area
  
  # Example usage to pass the assertions
  shape = Shape('Square', 10)
  assert shape.get_type() == 'Square'
  assert shape.get_area() == 10
  shape.set_area(20)
  assert shape.get_area() == 20