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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 send_mass_template_mail(subject_template, body_template, recipients, context=None):
 """ Renders an email subject and body using the given templates and context, then sends it to the given recipients list. The emails are send one-by-one. """

    if context:
        subject, body = render_mail_template(subject_template, body_template, context)
    else:
        subject, body = subject_template, body_template

    message_tuples = [(subject, body, conf.get('DEFAULT_FROM_EMAIL'), [r]) for r in recipients]

    send_mass_mail(message_tuples)