Convert png image bytes to numpy array

png_to_numpy.py

import numpy as np
from io import BytesIO
from PIL import Image

def png_bytes_to_numpy(png):
    """Convert png bytes to numpy array
    
    Example:  
    
    >>> fig = go.Figure(go.Scatter(x=[1], y=[1]))
    >>> plt.imshow(png_bytes_to_numpy(fig.to_image('png')))
    """
    return np.array(Image.open(BytesIO(png)))

i get this error
UnidentifiedImageError: cannot identify image file <_io.BytesIO object at 0x7e34b56d20c0>

how can i fix that error