Helper to configure pool options during DatabaseWrapper initialization.

def _set_up_pool_config(self):
    '''
    Helper to configure pool options during DatabaseWrapper initialization.
    '''
    self._max_conns = self.settings_dict['OPTIONS'].get('MAX_CONNS', pool_config_defaults['MAX_CONNS'])
    self._min_conns = self.settings_dict['OPTIONS'].get('MIN_CONNS', self._max_conns)
                
    self._test_on_borrow = self.settings_dict["OPTIONS"].get('TEST_ON_BORROW', 
                                                             pool_config_defaults['TEST_ON_BORROW'])
    if self._test_on_borrow:
        self._test_on_borrow_query = self.settings_dict["OPTIONS"].get('TEST_ON_BORROW_QUERY', 
                                                                       pool_config_defaults['TEST_ON_BORROW_QUERY'])
    else: 
        self._test_on_borrow_query = None