def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def encode(value):
    if isinstance(value, bytes):
        value = value.decode(errors="surrogateescape")

    for char in ("\\", "\n", "\t"):
        value = value.replace(
            char, char.encode(encoding="unicode-escape").decode()
        )

    return value