is_prime function using a prime sieve with runtime of O(sqrt n / log n)

prime_sieve.py

from typing import Optional

def smallest_positive_prime_factor(n: int) -> Optional[int]:
  N = abs(n)
  if N <= 1:
    return None
  m = 1 + int(N ** (1 / 2))
  checked = {d: False for d in range(2, m)}
  for d in range(2, m):
    if not checked[d]:
      if N % d == 0:
        return d
      for m in range(1, m // d):
        checked[d * m] = True
  return N
  
def is_prime(n: int) -> bool:
  return abs(n) == smallest_positive_prime_factor(n)