input: Write a python function to get the sum of two numbers from tkinter entry fields and display the result in a label.
  assert get_sum(3, 5) == "Sum is 8"
  assert get_sum(-1, 4) == "Sum is 3"
  assert get_sum(0, 0) == "Sum is 0"
output: def get_sum():
      import tkinter as tk
  
      def calculate_sum():
          num1 = int(entry1.get())
          num2 = int(entry2.get())
          result = num1 + num2
          result_label.config(text=f"Sum is {result}")
  
      root = tk.Tk()
      root.title("Sum Calculator")
  
      entry1 = tk.Entry(root)
      entry1.pack()
  
      entry2 = tk.Entry(root)
      entry2.pack()
  
      calculate_button = tk.Button(root, text="Calculate", command=calculate_sum)
      calculate_button.pack()
  
      result_label = tk.Label(root, text="Sum is ")
      result_label.pack()
  
      root.mainloop()