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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_regions_and_coremasks(self):
 """Generate a set of ordered paired region and core mask representations. .. note:: The region and core masks are ordered such that ``(region << 32) | core_mask`` is monotonically increasing. Consequently region and core masks generated by this method can be used with SCAMP's Flood-Fill Core Select (FFSC) method. Yields ------ (region, core mask) Pair of integers which represent a region of a SpiNNaker machine and a core mask of selected cores within that region. """

        region_code = ((self.base_x << 24) | (self.base_y << 16) |
                       (self.level << 16))

        # Generate core masks for any regions which are selected at this level
        # Create a mapping from subregion mask to core numbers
        subregions_cores = collections.defaultdict(lambda: 0x0)
        for core, subregions in enumerate(self.locally_selected):
            if subregions:  # If any subregions are selected on this level
                subregions_cores[subregions] |= 1 << core

        # Order the locally selected items and then yield them
        for (subregions, coremask) in sorted(subregions_cores.items()):
            yield (region_code | subregions), coremask

        if self.level < 3:
            # Iterate through the subregions and recurse, we iterate through in
            # the order which ensures that anything we yield is in increasing
            # order.
            for i in (4*x + y for y in range(4) for x in range(4)):
                subregion = self.subregions[i]
                if subregion is not None:
                    for (region, coremask) in \
                            subregion.get_regions_and_coremasks():
                        yield (region, coremask)