Adds Additional Constraints to the probnet dict.

        Parameters
        ----------
        criterion: <Element Constraint at AdditionalConstraints Node in XML>
            etree Element consisting Constraint tag.

        Examples
        -------
        >>> reader = ProbModelXMLReader()
        >>> reader.add_additionalconstraints(constraint)

def add_probnet_additionalconstraints(self, constraint):
        """
        Adds Additional Constraints to the probnet dict.

        Parameters
        ----------
        criterion: <Element Constraint at AdditionalConstraints Node in XML>
            etree Element consisting Constraint tag.

        Examples
        -------
        >>> reader = ProbModelXMLReader()
        >>> reader.add_additionalconstraints(constraint)
        """
        constraint_name = constraint.attrib['name']
        self.probnet['AdditionalConstraints'][constraint_name] = {}
        for argument in constraint.findall('Argument'):
            argument_name = argument.attrib['name']
            argument_value = argument.attrib['value']
            self.probnet['AdditionalConstraints'][constraint_name][argument_name] = argument_value