input: Write a function to take a radius input from the user and calculate the area of a circle. Use the value of Pi as 3.14. If the radius is empty or invalid, prompt the user to enter a valid value and return the calculated area of the circle.
  assert calculate_circle_area()==None
  assert calculate_circle_area()==None
  assert calculate_circle_area()==28.26
  assert calculate_circle_area()==50.24
  assert calculate_circle_area()==None
output: def calculate_circle_area():
      while True:
          radius = input("Enter the radius of the circle: ")
          if radius.strip() == "":
              continue
          try:
              radius = float(radius)
              if radius <= 0:
                  continue
              return 3.14 * radius * radius
          except ValueError:
              continue