Converts the tag type found in the root and converts them using the func
    and appends them to the values.

def __convert(root, tag, values, func):
    """Converts the tag type found in the root and converts them using the func
    and appends them to the values.
    """
    elements = root.getElementsByTagName(tag)

    for element in elements:
        converted = func(element)

        # Append to the list
        __append_list(values, converted)