code: def applyKeyMapping(self, mapping):
  		
  		for coltype, colname in zip(self.columntypes, self.columnnames):
  			if coltype in ligolwtypes.IDTypes and (self.next_id is None or colname != self.next_id.column_name):
  				column = self.getColumnByName(colname)
  				for i, old in enumerate(column):
  					try:
  						column[i] = mapping[old]
  					except KeyError:
  						pass
docs: Used as the second half of the key reassignment algorithm.
  		Loops over each row in the table, replacing references to
  		old row keys with the new values from the mapping.