code: def _GetDistinctValues(self, field_name):
      
      self._cursor.execute(
          'SELECT {0:s}, COUNT({0:s}) FROM log2timeline GROUP BY {0:s}'.format(
              field_name))
  
      result = {}
      row = self._cursor.fetchone()
      while row:
        if row[0]:
          result[row[0]] = row[1]
        row = self._cursor.fetchone()
      return result
docs: Query database for unique field types.
  
      Args:
        field_name (str): name of the filed to retrieve.
  
      Returns:
        dict[str, int]: counts of field types by name.