Sets the index for this combobox to the inputed schema instance.
        
        :param      schema      <orb.TableSchema>
        
        :return     <bool> success

def setCurrentSchema( self, schema ):
        """
        Sets the index for this combobox to the inputed schema instance.
        
        :param      schema      <orb.TableSchema>
        
        :return     <bool> success
        """
        if ( not schema in self._schemas ):
            return False
        
        index = self._schemas.index(schema)
        self.setCurrentIndex(index)
        return True