'Executes a SELECT query on the named table, which is expected to
return a single row, returning a single column from it.
Args:
table : string giving the table name
keyvalues : dict of column names and values to select the row with
retcol : string giving the name of the column to return'

def _simple_select_one_onecol(self, table, keyvalues, retcol, allow_none=False, desc='_simple_select_one_onecol'):

    return self.runInteraction(desc, self._simple_select_one_onecol_txn, table, keyvalues, retcol, allow_none=allow_none)
