code: def is_unique(self, table_name, sample, unique_fields=None):
          
          try:
              eid = find_unique(self.table(table_name),
                                sample=sample,
                                unique_fields=unique_fields)
          except:
              return False
          else:
              return eid is not None
docs: Return True if an item with the value of `unique_fields`
          from `data` is unique in the table with `table_name`.
          False if no sample is found or more than one is found.
  
          See function `find_unique` for more details.
  
          Parameters
          ----------
          table_name: str
  
          sample: dict
              Sample data for query
  
          unique_fields: str or list of str
  
          Returns
          -------
          is_unique: bool