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 post(txt, contact, parenttype=None, notify=False, subject=None):
	"""post message"""

	d = frappe.new_doc('Communication')
	d.communication_type = 'Notification' if parenttype else 'Chat'
	d.subject = subject
	d.content = txt
	d.reference_doctype = 'User'
	d.reference_name = contact
	d.sender = frappe.session.user
	d.insert(ignore_permissions=True)

	delete_notification_count_for("Messages")

	if notify and cint(notify):
		if contact==frappe.session.user:
			_notify([user.name for user in get_enabled_system_users()], txt)
		else:
			_notify(contact, txt, subject)

	return d