def copy ( self ) : out = type ( self ) ( ) for series in self : out . append ( series . copy ( ) ) return out
python force list reference to be copy
Return a copy of this list with each element copied to new memory
def copy(self):
        """Return a copy of this list with each element copied to new memory
        """
        out = type(self)()
        for series in self:
            out.append(series.copy())
        return out