'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
retcols : list of strings giving the names of the columns to return
allow_none : If true, return None instead of failing if the SELECT
statement returns no rows'

def _simple_select_one(self, table, keyvalues, retcols, allow_none=False, desc='_simple_select_one'):

    return self.runInteraction(desc, self._simple_select_one_txn, table, keyvalues, retcols, allow_none)
