def from_json(json_data, key):
    """Extract values from JSON data.

    :arg dict json_data: The JSON data
    :arg str key: Key to get data for.

    :Returns: The value of `key` from `json_data`, or None if `json_data`
        does not contain `key`.

    """
    if key in json_data:
        return json_data[key]
    return None