input: Write a python function to calculate the area of a given shape.
  assert calculate_area("rectangle") == 20.0  # Assuming input length=5 and width=4
  assert calculate_area("triangle") == 10.0   # Assuming input base=5 and height=4
  assert calculate_area("circle") == 50.26548245743669  # Assuming input radius=4
  assert calculate_area("hexagon") == "This shape is not supported"
output: import math
  
  def calculate_area(shape):
      if shape == "rectangle":
          length = 5
          width = 4
          return length * width
      elif shape == "triangle":
          base = 5
          height = 4
          return 0.5 * base * height
      elif shape == "circle":
          radius = 4
          return math.pi * radius * radius
      else:
          return "This shape is not supported"