Why do I get a function call before assignment error?

class MuscleCar():
    list = ["4 wheels", "big engine", "2 doors", "high-speed", "4 seat"]
    "Class Attributes:"
    hp = 300
    spoiler = False

    def __init__(self,make, model, year, top_speed):
            #Initializer
        self.make = make
        self.model = model
        self.year = year
        self.is_moving = False
        self.gas = 100
        self.top_speed = top_speed
#Method
#Stop
    def stop(self):
        print("The car has stopped, but the breaks had to be slammed!")
        if self.is_moving:
            print("The car has stopped!What a relief!")
            self.is_moving = False
        else:
            ("The car has already stopped!")

    def go(self, speed):
        if self.use_gas():
            if not self.is_moving:
                print("The car is in motion.")
                self.is_moving = True
            print(f"The car is going {speed} MPH")
        else:
            print("Dawg, we already ran out of gas. Now we have to push it to a gas station.")
            self.stop()

    def use_gas(self):
        gas -= 50
        if gas <=0:
            return False
        else:
            return True

mCar = MuscleCar('Dodge', 'Charger', 1970, 150)
mCar2 = MuscleCar('Pontiac', 'GTO Judge', 1969, 150)
print(mCar.make+mCar.model)
print(mCar2.make+mCar2.model)

mCar.go(20)
mCar.go(90)
mCar.stop()
print(mCar)
mCar.stop()
mCar2.go(100)
    #print(mCar.year)
"""MuscleCar()
mCar = MuscleCar()
print(MuscleCar, mCar)
"Class Attributes:"
print(mCar.list)
print(mCar.list.append("exaust"))
mCar.list.extend([", exaust"])
print(mCar.hp)
print(MuscleCar.hp)
"""

#Instance Attributes:
#mCar.list.extend([", exaust"])