input: Write a python function to calculate the monthly loan payment given the loan amount, annual interest rate, and loan period.
  assert loan_payment(10000, 5.5, 5) == 190.29583580304586
  assert loan_payment(20000, 7.2, 10) == 233.83064345349006
  assert loan_payment(5000, 3.5, 3) == 146.8578583813311
output: def loan_payment(loan_amount, annual_interest_rate, loan_period):
      monthly_interest_rate = annual_interest_rate / 100 / 12
      number_of_payments = loan_period * 12
      monthly_payment = (loan_amount * monthly_interest_rate) / (1 - (1 + monthly_interest_rate) ** -number_of_payments)
      return monthly_payment