<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_labels(self, depth=None):
 """ Returns a list with a copy of the labels in this cell. Parameters depth : integer or ``None`` If not ``None``, defines from how many reference levels to retrieve labels from. Returns ------- out : list of ``Label`` List containing the labels in this cell and its references. """

        labels = libCopy.deepcopy(self.labels)
        if depth is None or depth > 0:
            for element in self.elements:
                if isinstance(element, CellReference):
                    labels.extend(
                        element.get_labels(None if depth is None else depth -
                                           1))
                elif isinstance(element, CellArray):
                    labels.extend(
                        element.get_labels(None if depth is None else depth -
                                           1))
        return labels