Format a value accoding to its type.

    Unicode is supported:

    >>> hrow = ['\u0431\u0443\u043a\u0432\u0430', '\u0446\u0438\u0444\u0440\u0430'] ; \
        tbl = [['\u0430\u0437', 2], ['\u0431\u0443\u043a\u0438', 4]] ; \
        good_result = '\\u0431\\u0443\\u043a\\u0432\\u0430      \\u0446\\u0438\\u0444\\u0440\\u0430\\n-------  -------\\n\\u0430\\u0437             2\\n\\u0431\\u0443\\u043a\\u0438           4' ; \
        tabulate(tbl, headers=hrow) == good_result
    True

def _format(val, valtype, floatfmt, missingval="", has_invisible=True):
    """Format a value accoding to its type.

    Unicode is supported:

    >>> hrow = ['\u0431\u0443\u043a\u0432\u0430', '\u0446\u0438\u0444\u0440\u0430'] ; \
        tbl = [['\u0430\u0437', 2], ['\u0431\u0443\u043a\u0438', 4]] ; \
        good_result = '\\u0431\\u0443\\u043a\\u0432\\u0430      \\u0446\\u0438\\u0444\\u0440\\u0430\\n-------  -------\\n\\u0430\\u0437             2\\n\\u0431\\u0443\\u043a\\u0438           4' ; \
        tabulate(tbl, headers=hrow) == good_result
    True

    """
    if val is None:
        return missingval

    if valtype in [int, _long_type, _text_type]:
        return "{0}".format(val)
    elif valtype is _binary_type:
        try:
            return _text_type(val, "ascii")
        except TypeError:
            return _text_type(val)
    elif valtype is float:
        is_a_colored_number = has_invisible and isinstance(val, (_text_type, _binary_type))
        if is_a_colored_number:
            raw_val = _strip_invisible(val)
            formatted_val = format(float(raw_val), floatfmt)
            return val.replace(raw_val, formatted_val)
        else:
            return format(float(val), floatfmt)
    else:
        return "{0}".format(val)