'GetGraphics'のエラーを解決したい

前提・実現したいこと

ここに質問の内容を詳しく書いてください。
pyxelの9行目でplayerの画像(player.png)を表示させようとしたら、'GetGraphics'のエラーが出ました。アドバイスを頂きたいです。

発生している問題・エラーメッセージ

pyxel error: uninitialized function call in 'GetGraphics'

該当のソースコード

import pyxel

class App:
    def init(self):
        pyxel.init(160, 120, caption="Invadors game",
        palette=[1],quit_key=pyxel.KEY_NONE)

#Player
pyxel.image(0).load(0, 0, "./player.png")
playerX,playerY = 370, 480
playerX_change = 0

pyxel.Sound(0).set('laser.wav').play()

#Enemy
enemyImg = pyxel.image.load('enemy.png')
enemyX = random.randint(0, 736)
enemyY = random.randint(50, 150)
enemyX_change, enemyY_change = 4, 40

#Bullet
bulletImg = pyxel.image.load('bullet.png')
bulletX, bulletY = 0, 480
bulletX_change, bulletY_change = 0, 3
bullet_state = 'ready'


#Score
score_value = 0

def player(x, y):
    screen.blit(playerImg, (x, y))

def enemy(x, y):
    screen.blit(enemyImg, (x, y))
    
def fire_bullet(x, y):
    global bullet_state
    bullet_state = 'fire'
    screen.blit(bulletImg, (x + 16, y + 10))
    
def isCollision(enemyX, enemyY, bulletX, bulletY):
    distance = math.sqrt(math.pow(enemyX - bulletX, 2) + math.pow(enemyY - bulletY, 2))
    if distance < 27:
        return true
    else:
        return False

running = True
while running: 
    screen.fill((0, 0, 0))
      #font = pyxel.font.SysFont(None, 80)
      #message = font.render('Hello World', False, (255, 255, 255))
      #screen.blit(message, (20,50))
    for event in pyxel.event.get():
            if event.type == pyxel.QUIT:
                 running = False
if event.type == pyxel.KEYDOWN:
    if event.key == pyxel.K_LEFT:
        playerX_change = -1.5
    if event.key == pyxel.K_RIGHT:
        playerX_change = 1.5
    if event.key == pyxel.K_SPACE:
       if bullet_state == 'ready':
            bulletX = playerX
            fire_bullet(bulletX, bulletY)
            
    if event.type == pyxel.KEYUP:
            if event.key == pyxel.K_LEFT or event.key == pyxel.K_RIGHT:
                playerX_change = 0
   
    #Player
    playerX += playerX_change
    if playerX <= 0:
         playerX = 0
    elif playerX >= 736:
        playerX = 736
     
    #Enemy
    if enemy > 440:
         pass
    enemyX += enemyX_change
    if enemyX <= 0:
        enemyX_change = 4 #go right if come to the leftend
        enemyY += enemyY_change
    elif enemyX >= 736:
        enemyX_change = -4 #go left if come to the rightend
        enemyY += enemyY_change
    
    collision = isCollision(enemyX, enemyY, bulletX, bulletY)
    if collosion:
        bulletY = 480
        bullet_state = 'ready'
        score_value += 1
        enemyX = random.randint(0, 736)
        enemyY = random.randint(50, 150)
    
    #bullet Movement
    if bulletY <=0:
        bulletY = 480
        bullet_state = 'ready'
        
    if bullet_state == 'fire':
        fire_bullet(bulletX, bulletY)
        bulletY -= bulletY_change
    
    
    
    #Score
    font = pyxel.font.SysFont(None, 32) #creating fonts 'None' is default
    score = font.render("Score: {str(score_value)}", True, (255,255,255))
    screen.blit(score, (20,50))
    
    
    player(playerX, playerY)
    enemy(enemyX, enemyY)
    
    pyxel.display.update()

App()