def to_special_value(self, value):
if value == self.spdx_namespace.none:<EOL><INDENT>return utils.SPDXNone()<EOL><DEDENT>elif value == self.spdx_namespace.noassertion:<EOL><INDENT>return utils.NoAssert()<EOL><DEDENT>elif value == self.spdx_namespace.unknown:<EOL><INDENT>return utils.UnKnown()<EOL><DEDENT>else:<EOL><INDENT>return value<EOL><DEDENT>
Checks if value is a special SPDX value such as
        NONE, NOASSERTION or UNKNOWN if so returns proper model.
        else returns value