human
Complete the below
def build(version=None, requirements=None):

    ''''Return the built contents of the letsencrypt-auto script.
    :arg version: The version to attach to the script. Default: the version of
    the certbot package
    :arg requirements: The contents of the requirements file to embed. Default:
    contents of dependency-requirements.txt, letsencrypt-requirements.txt,
    and certbot-requirements.txt'
    '''

=====
Give me a the Python code you requested?
assistant
#Here is the Python code you requested.
    special_replacements = {'LE_AUTO_VERSION': (version or certbot_version(DIR))}
    if requirements:
        special_replacements['dependency-requirements.txt'] = ''
        special_replacements['letsencrypt-requirements.txt'] = ''
        special_replacements['certbot-requirements.txt'] = requirements
    def replacer(match):
        token = match.group(1)
        if (token in special_replacements):
            return special_replacements[token]
        else:
            return file_contents(join(DIR, 'pieces', token))
    return re.sub('{{\\s*([A-Za-z0-9_./-]+)\\s*}}', replacer, file_contents(join(DIR, 'letsencrypt-auto.template')))