[Python] Implementing abstract classes

I am a beginner in Python coding and I try to learn abstract classes. I have a problem with implementing two exams which extend abstract class Exam, defining contract for diagnostic test.

class Person:
def __init__(self, name: str, age: int):
self.name = name
self.age = age

class Patient(Person):
def __init__(self, name: str, age: int, id: str, symptoms: list\[str\], cholesterol: float, iron_level: float):
super().__init__(name, age)
self.id = id
self.symptoms = symptoms
self.cholesterol = cholesterol
self.iron_level = iron_level\`

class CholesterolExam(Exam):
def __init__(self):
super().__init__('Cholesterol Exam')

def perform_exam(self,cholesterol_exam):
if cholesterol_exam >= 200:
return False
return True

class IronLevelExam(Exam):
def __init__(self):
super().__init__('Iron Exam')

def perform_exam(self,iron_level_exam):
if iron_level_exam>50 and iron_level_exam<170:
return True

class Test03(unittest.TestCase):
def test_doctor(self):
cholesterol_exam = CholesterolExam()
iron_level_exam = IronLevelExam()
p = Patient('John', 30, '001', ['cough', 'fever'], 180, 300)
cholesterol_exam_result, iron_exam_result = [exam.perform_exam(p) for exam in [cholesterol_exam, iron_level_exam]]

self.assertTrue(cholesterol_exam_result)
self.assertFalse(iron_exam_result)

test(Test03)


I get the error message:

line 32, in test_doctor cholesterol_exam_result, iron_exam_result = [exam.perform_exam(p) for exam in [cholesterol_exam, iron_level_exam]]

line 12, in perform_exam if cholesterol_exam >= 200:

TypeError: '>=' not supported between instances of 'Patient' and 'int'
​

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