def return_attr(self, attr, labels=None):
        """return the attributes for each channels.

        Parameters
        ----------
        attr : str
            attribute specified in Chan.attr.keys()

        """
        all_labels = self.return_label()

        if labels is None:
            labels = all_labels

        all_attr = []
        for one_label in labels:
            idx = all_labels.index(one_label)
            try:
                all_attr.append(self.chan[idx].attr[attr])
            except KeyError:
                possible_attr = ', '.join(self.chan[idx].attr.keys())
                lg.debug('key "{}" not found, '.format(attr) +
                         'possible keys are {}'.format(possible_attr))
                all_attr.append(None)

        return all_attr
def return_attr ( self , attr , labels = None ) : all_labels = self . return_label ( ) if labels is None : labels = all_labels all_attr = [ ] for one_label in labels : idx = all_labels . index ( one_label ) try : all_attr . append ( self . chan [ idx ] . attr [ attr ] ) except KeyError : possible_attr = ', ' . join ( self . chan [ idx ] . attr . keys ( ) ) lg . debug ( 'key "{}" not found, ' . format ( attr ) + 'possible keys are {}' . format ( possible_attr ) ) all_attr . append ( None ) return all_attr
return the attributes for each channels.

        Parameters
        ----------
        attr : str
            attribute specified in Chan.attr.keys()