How to use the rez.vendor.pyparsing.pyparsing.Literal function in rez

class InvalidRequirement(ValueError):
    """
    An invalid requirement was found, users should refer to PEP 508.
    """


ALPHANUM = Word(string.ascii_letters + string.digits)

LBRACKET = L("[").suppress()
RBRACKET = L("]").suppress()
LPAREN = L("(").suppress()
RPAREN = L(")").suppress()
COMMA = L(",").suppress()
SEMICOLON = L(";").suppress()
AT = L("@").suppress()

PUNCTUATION = Word("-_.")
IDENTIFIER_END = ALPHANUM | (ZeroOrMore(PUNCTUATION) + ALPHANUM)
IDENTIFIER = Combine(ALPHANUM + ZeroOrMore(IDENTIFIER_END))

NAME = IDENTIFIER("name")
EXTRA = IDENTIFIER

URI = Regex(r"[^ ]+")("url")
URL = AT + URI

EXTRAS_LIST = EXTRA + ZeroOrMore(COMMA + EXTRA)
EXTRAS = (LBRACKET + Optional(EXTRAS_LIST) + RBRACKET)("extras")

VERSION_PEP440 = Regex(Specifier._regex_str, re.VERBOSE | re.IGNORECASE)
VERSION_LEGACY = Regex(LegacySpecifier._regex_str, re.VERBOSE | re.IGNORECASE)

| L("platform.python_implementation")  # PEP-345
    | L("python_implementation")  # PEP-345
    | L("extra")  # undocumented setuptools legacy
)
ALIASES = {
    "os.name": "os_name",
    "sys.platform": "sys_platform",
    "platform.version": "platform_version",
    "platform.machine": "platform_machine",
    "platform.python_implementation": "platform_python_implementation",
    "python_implementation": "platform_python_implementation",
}
VARIABLE.setParseAction(lambda s, l, t: Variable(ALIASES.get(t[0], t[0])))

VERSION_CMP = (
    L("===") | L("==") | L(">=") | L("<=") | L("!=") | L("~=") | L(">") | L("<")
)

MARKER_OP = VERSION_CMP | L("not in") | L("in")
MARKER_OP.setParseAction(lambda s, l, t: Op(t[0]))

MARKER_VALUE = QuotedString("'") | QuotedString('"')
MARKER_VALUE.setParseAction(lambda s, l, t: Value(t[0]))

BOOLOP = L("and") | L("or")

MARKER_VAR = VARIABLE | MARKER_VALUE

MARKER_ITEM = Group(MARKER_VAR + MARKER_OP + MARKER_VAR)
MARKER_ITEM.setParseAction(lambda s, l, t: tuple(t[0]))

LPAREN = L("(").suppress()

| L("platform_python_implementation")
    | L("implementation_name")
    | L("python_full_version")
    | L("platform_release")
    | L("platform_version")
    | L("platform_machine")
    | L("platform_system")
    | L("python_version")
    | L("sys_platform")
    | L("os_name")
    | L("os.name")
    | L("sys.platform")  # PEP-345
    | L("platform.version")  # PEP-345
    | L("platform.machine")  # PEP-345
    | L("platform.python_implementation")  # PEP-345
    | L("python_implementation")  # PEP-345
    | L("extra")  # undocumented setuptools legacy
)
ALIASES = {
    "os.name": "os_name",
    "sys.platform": "sys_platform",
    "platform.version": "platform_version",
    "platform.machine": "platform_machine",
    "platform.python_implementation": "platform_python_implementation",
    "python_implementation": "platform_python_implementation",
}
VARIABLE.setParseAction(lambda s, l, t: Variable(ALIASES.get(t[0], t[0])))

VERSION_CMP = (
    L("===") | L("==") | L(">=") | L("<=") | L("!=") | L("~=") | L(">") | L("<")
)

MARKER_OP = VERSION_CMP | L("not in") | L("in")
MARKER_OP.setParseAction(lambda s, l, t: Op(t[0]))

MARKER_VALUE = QuotedString("'") | QuotedString('"')
MARKER_VALUE.setParseAction(lambda s, l, t: Value(t[0]))

BOOLOP = L("and") | L("or")

MARKER_VAR = VARIABLE | MARKER_VALUE

MARKER_ITEM = Group(MARKER_VAR + MARKER_OP + MARKER_VAR)
MARKER_ITEM.setParseAction(lambda s, l, t: tuple(t[0]))

LPAREN = L("(").suppress()
RPAREN = L(")").suppress()

MARKER_EXPR = Forward()
MARKER_ATOM = MARKER_ITEM | Group(LPAREN + MARKER_EXPR + RPAREN)
MARKER_EXPR << MARKER_ATOM + ZeroOrMore(BOOLOP + MARKER_EXPR)

MARKER = stringStart + MARKER_EXPR + stringEnd


def _coerce_parse_result(results):
    if isinstance(results, ParseResults):
        return [_coerce_parse_result(i) for i in results]
    else:
        return results


def _format_marker(marker, first=True):

VARIABLE = (
    L("implementation_version")
    | L("platform_python_implementation")
    | L("implementation_name")
    | L("python_full_version")
    | L("platform_release")
    | L("platform_version")
    | L("platform_machine")
    | L("platform_system")
    | L("python_version")
    | L("sys_platform")
    | L("os_name")
    | L("os.name")
    | L("sys.platform")  # PEP-345
    | L("platform.version")  # PEP-345
    | L("platform.machine")  # PEP-345
    | L("platform.python_implementation")  # PEP-345
    | L("python_implementation")  # PEP-345
    | L("extra")  # undocumented setuptools legacy
)
ALIASES = {
    "os.name": "os_name",
    "sys.platform": "sys_platform",
    "platform.version": "platform_version",
    "platform.machine": "platform_machine",
    "platform.python_implementation": "platform_python_implementation",
    "python_implementation": "platform_python_implementation",
}
VARIABLE.setParseAction(lambda s, l, t: Variable(ALIASES.get(t[0], t[0])))

VERSION_CMP = (
    L("===") | L("==") | L(">=") | L("<=") | L("!=") | L("~=") | L(">") | L("<")

def serialize(self):
        return str(self)


class Value(Node):
    def serialize(self):
        return '"{0}"'.format(self)


class Op(Node):
    def serialize(self):
        return str(self)


VARIABLE = (
    L("implementation_version")
    | L("platform_python_implementation")
    | L("implementation_name")
    | L("python_full_version")
    | L("platform_release")
    | L("platform_version")
    | L("platform_machine")
    | L("platform_system")
    | L("python_version")
    | L("sys_platform")
    | L("os_name")
    | L("os.name")
    | L("sys.platform")  # PEP-345
    | L("platform.version")  # PEP-345
    | L("platform.machine")  # PEP-345
    | L("platform.python_implementation")  # PEP-345
    | L("python_implementation")  # PEP-345

return str(self)


VARIABLE = (
    L("implementation_version")
    | L("platform_python_implementation")
    | L("implementation_name")
    | L("python_full_version")
    | L("platform_release")
    | L("platform_version")
    | L("platform_machine")
    | L("platform_system")
    | L("python_version")
    | L("sys_platform")
    | L("os_name")
    | L("os.name")
    | L("sys.platform")  # PEP-345
    | L("platform.version")  # PEP-345
    | L("platform.machine")  # PEP-345
    | L("platform.python_implementation")  # PEP-345
    | L("python_implementation")  # PEP-345
    | L("extra")  # undocumented setuptools legacy
)
ALIASES = {
    "os.name": "os_name",
    "sys.platform": "sys_platform",
    "platform.version": "platform_version",
    "platform.machine": "platform_machine",
    "platform.python_implementation": "platform_python_implementation",
    "python_implementation": "platform_python_implementation",
}
VARIABLE.setParseAction(lambda s, l, t: Variable(ALIASES.get(t[0], t[0])))

"platform.python_implementation": "platform_python_implementation",
    "python_implementation": "platform_python_implementation",
}
VARIABLE.setParseAction(lambda s, l, t: Variable(ALIASES.get(t[0], t[0])))

VERSION_CMP = (
    L("===") | L("==") | L(">=") | L("<=") | L("!=") | L("~=") | L(">") | L("<")
)

MARKER_OP = VERSION_CMP | L("not in") | L("in")
MARKER_OP.setParseAction(lambda s, l, t: Op(t[0]))

MARKER_VALUE = QuotedString("'") | QuotedString('"')
MARKER_VALUE.setParseAction(lambda s, l, t: Value(t[0]))

BOOLOP = L("and") | L("or")

MARKER_VAR = VARIABLE | MARKER_VALUE

MARKER_ITEM = Group(MARKER_VAR + MARKER_OP + MARKER_VAR)
MARKER_ITEM.setParseAction(lambda s, l, t: tuple(t[0]))

LPAREN = L("(").suppress()
RPAREN = L(")").suppress()

MARKER_EXPR = Forward()
MARKER_ATOM = MARKER_ITEM | Group(LPAREN + MARKER_EXPR + RPAREN)
MARKER_EXPR << MARKER_ATOM + ZeroOrMore(BOOLOP + MARKER_EXPR)

MARKER = stringStart + MARKER_EXPR + stringEnd