'Retrieve the latest value set for a subject\'s attribute.
Args:
subject: The subject URN.
attribute: The attribute.
token: The security token used in this call.
Returns:
A (string, timestamp in microseconds) stored in the bigtable
cell, or (None, 0).
Raises:
AccessError: if anything goes wrong.'

def Resolve(self, subject, attribute, token=None):

    subject = utils.SmartStr(subject)
    attribute = utils.SmartStr(attribute)
    (family, column) = self.GetFamilyColumn(attribute)
    col_filter = row_filters.ColumnRangeFilter(family, start_column=column, end_column=column)
    latest_filter = row_filters.CellsColumnLimitFilter(1)
    row_filter = row_filters.RowFilterChain(filters=[col_filter, latest_filter])
    row_data = self.table.read_row(subject, filter_=row_filter)
    if row_data:
        for cell in row_data.cells[family][column]:
            return (self.Decode(attribute, cell.value), self.DatetimeToMicroseconds(cell.timestamp))
    return (None, 0)
