code: def put(self, key, value):
          
          # check if we're maxed out first
          if self.size() == self._maxsize:
              # need to kick something out...
              self.delete(self.last())
          LRUCache.put(self, key, value)
docs: >>> c = FixedSizeLRUCache(maxsize=5)
          >>> c.put(1, 'one')
          >>> c.get(1)
          'one'
          >>> c.size()
          1
          >>> c.put(2, 'two')
          >>> c.put(3, 'three')
          >>> c.put(4, 'four')
          >>> c.put(5, 'five')
          >>> c.get(5)
          'five'
          >>> c.size()
          5
          >>> c.put(6, 'six')
          >>> c.size()
          5
          >>> c.get(1)
          Traceback (most recent call last):
              ...
          KeyError: 1
          >>> c.get(2)
          'two'
          >>> c.put(7, 'seven')
          >>> c.get(2)
          'two'
          >>> c.get(3)
          Traceback (most recent call last):
              ...
          KeyError: 3