docs: 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