def do_prepend(a, b):
    """
    Adds the specified string to the beginning of another string.
    https://github.com/Shopify/liquid/blob/b2feeacbce8e4a718bde9bc9fa9d00e44ab32351/test/integration/standard_filter_test.rb#L502
    """
    return '{}{}'.format(b, a)