code: def find_unique(table, sample, unique_fields=None):
      
      res = search_unique(table, sample, unique_fields)
      if res is not None:
          return res.eid
      else:
          return res
docs: Search in `table` an item with the value of the `unique_fields` in the `sample` sample.
      Check if the the obtained result is unique. If nothing is found will return an empty list,
      if there is more than one item found, will raise an IndexError.
  
      Parameters
      ----------
      table: tinydb.table
  
      sample: dict
          Sample data
  
      unique_fields: list of str
          Name of fields (keys) from `data` which are going to be used to build
          a sample to look for exactly the same values in the database.
          If None, will use every key in `data`.
  
      Returns
      -------
      eid: int
          Id of the object found with same `unique_fields`.
          None if none is found.
  
      Raises
      ------
      MoreThanOneItemError
          If more than one example is found.