input: Write a function to determine if a given number is a prime number. The function should return True if the number is prime, otherwise return False. If the given number is less than or equal to 1, the function should return False.
  
  def is_prime(num):
      if num <= 1:
          return False
      for i in range(2, int(num**0.5) + 1):
          if num % i == 0:
              return False
      return True
  
  assert is_prime(17)==True
  assert is_prime(15)==False
  assert is_prime(2)==True
  assert is_prime(-5)==False
  assert is_prime(1)==False
output: def is_prime(num):
      if num <= 1:
          return False
      for i in range(2, int(num**0.5) + 1):
          if num % i == 0:
              return False
      return True