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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 validate_nb(nb):
 """ Validate that given notebook JSON is importable - Check for nbformat == 4 - Check that language is python Do not re-implement nbformat here :D """

    if nb['nbformat'] != 4:
        return False

    language_name = (nb.get('metadata', {})
        .get('kernelspec', {})
        .get('language', '').lower())
    return language_name == 'python'