<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _is_video(filepath) -> bool: """Check filename extension to see if it's a video file."""

    if os.path.exists(filepath):  # Could be broken symlink
        extension = os.path.splitext(filepath)[1]
        return extension in ('.mkv', '.mp4', '.avi')
    else:
        return False