Update MapSparse.py

Qualification for Cython.

Author: soft9000

MapSparse.py

@@ -43,7 +43,7 @@ def is_null(self):
             '''
             See if this AREA has anything important.
             '''
-            dum = Area()
+            dum = SparseMap.Area()
             return dum.name == self.name and \
                 dum.number == self.number and \
                 len(dum.objs) == len(self._pieces)
@@ -75,7 +75,7 @@ def get_map(self)->list:
 
         def __str__(self):
             result = ''
-            for line in get_map():
+            for line in self.get_map():
                 result += ''.join(line)
                 result += '\n'
             return result
@@ -234,4 +234,4 @@ def plot_ones_based(self, ones_based, xpos, ypos, glyph):
         Add an item to a MAP using the 1's based AREA identifier.
         Coordinates here are ONES based.
         '''
-        return self.plot(ones_based, xpos -1, ypos -1, glyph)
+        return self.plot(ones_based, xpos -1, ypos -1, glyph)