Short version of model name

        Dictionary defined in ``populations.py``::

            SHORT_MODELNAMES = {'Planets':'pl',
                    'EBs':'eb',
                    'HEBs':'heb',
                    'BEBs':'beb',
                    'Blended Planets':'bpl',
                    'Specific BEB':'sbeb',
                    'Specific HEB':'sheb'}

def modelshort(self):
        """
        Short version of model name

        Dictionary defined in ``populations.py``::

            SHORT_MODELNAMES = {'Planets':'pl',
                    'EBs':'eb',
                    'HEBs':'heb',
                    'BEBs':'beb',
                    'Blended Planets':'bpl',
                    'Specific BEB':'sbeb',
                    'Specific HEB':'sheb'}


        """
        try:
            name = SHORT_MODELNAMES[self.model]

            #add index if specific model is indexed
            if hasattr(self,'index'):
                name += '-{}'.format(self.index)

            return name

        except KeyError:
            raise KeyError('No short name for model: %s' % self.model)