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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 sanitize_filename(filename):
 """ Make sure filenames are valid paths. Returns: str: """

    sanitized_filename = re.sub(r'[/\\:*?"<>|]', '-', filename)
    sanitized_filename = sanitized_filename.replace('&', 'and')
    sanitized_filename = sanitized_filename.replace('"', '')
    sanitized_filename = sanitized_filename.replace("'", '')
    sanitized_filename = sanitized_filename.replace("/", '')
    sanitized_filename = sanitized_filename.replace("\\", '')

    # Annoying.
    if sanitized_filename[0] == '.':
        sanitized_filename = u'dot' + sanitized_filename[1:]

    return sanitized_filename