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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 normalize_placeholders(arg, inject_quotes=False):
 """ Normalize placeholders' names so that the template can be ingested into Jinja template engine. - Jinja does not accept numbers as placeholder names, so add a "_" before the numbers to make them valid placeholder names. - Surround placeholders expressions with "" so we can preserve spaces inside the positional arguments. Args: arg: The string to process. inject_qoutes: True if we want to surround placeholders with a pair of quotes. Returns: A processed string where placeholders are surrounded by "" and numbered placeholders are prepended with "_". """

    number_placeholders = re.findall(r'{{\s*\d+\s*}}', arg)
    for number_placeholder in number_placeholders:
        number = re.search(r'\d+', number_placeholder).group()
        arg = arg.replace(number_placeholder, '{{_' + number + '}}')

    return arg.replace('{{', '"{{').replace('}}', '}}"') if inject_quotes else arg