My sh*tting code to simplify a symbolic expression in SageMath over GF(p)

GF_simplify.py

import sage
from sage.all_cmdline import *   # import sage library
from sage.symbolic.operators import add_vararg, mul_vararg

def GF_simplify(_expr, p=2):
  expr = expand(_expr)
  if expr.operator() != add_vararg:
    raise Exception('Can only simplify a sum over products.')

  result = None
  for term in expr.operands():
    ignore_term = False
    if term.operator() == mul_vararg:
      for subt in term.operands():
        if subt.is_integer():
          n = subt.pyobject()
          if n % p == 0:
            ignore_term = True

    if not ignore_term:
      if result is None:
        result = term
      else:
        result += term

  return result