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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_language_key(obj, key):
 """Validate all nested "language" key in `obj`. Args: obj (dict):
 dictionary whose "language" key is to be validated. Returns: None: validation successful Raises: ValidationError: will raise exception in case language is not valid. """

    backend = bigchaindb.config['database']['backend']

    if backend == 'localmongodb':
        data = obj.get(key, {})
        if isinstance(data, dict):
            validate_all_values_for_key_in_obj(data, 'language', validate_language)
        elif isinstance(data, list):
            validate_all_values_for_key_in_list(data, 'language', validate_language)