code: def models_with_unique_column(meta, exclude_single_pk=True, exclude_multi_pk=True):
      
      models_with_potential_pk = {}
      fields_distinct = {}
      for model_name, model_fields in meta.iteritems():
          if exclude_single_pk and model_fields['Meta']['primary_key']:
                  continue
          fields_distinct = []
          for field_name, field in model_fields.iteritems():
              if field_name is 'Meta':
                  continue
              if float(field.get('fraction_distinct', 0)) == 1.:
                  fields_distinct += [field_name]
          # if any(not field['primary_key'] and field['num_distinct'] == 1 for field_name, field in model_fields.iteritems() if field is not 'Meta'):
          if (not exclude_multi_pk and fields_distinct) or len(fields_distinct) == 1:
              models_with_potential_pk[model_name] = fields_distinct
      return models_with_potential_pk
docs: Return a list of model names for models that have at least 1 field that has all distinct values (could be used as primary_key)