Method __add__

pattern/db/__init__.py:1761–1762

(self, datasheet)

    # datasheet1 = [[...],[...]] + datasheet2
    # datasheet1 += datasheet2
    def __add__(self, datasheet):
        m = self.copy(); m.extend(datasheet); return m
    def __radd__(self, datasheet):
        m = Datasheet(datasheet); m.extend(self); return m
    def __iadd__(self, datasheet):