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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def lazy_load_font(font_size=default_font_size):
 """ Lazy loading font according to system platform """

    if font_size not in _font_cache:
        if _platform.startswith("darwin"):
            font_path = "/Library/Fonts/Arial.ttf"
        elif _platform.startswith("linux"):
            font_path = "/usr/share/fonts/truetype/ubuntu-font-family/UbuntuMono-R.ttf"
        elif _platform.startswith("win32"):
            font_path = "C:\\Windows\\Fonts\\arial.ttf"
        _font_cache[font_size] = ImageFont.truetype(font_path, font_size)
    return _font_cache[font_size]