def _cache(self, key, val):
        if self.mode == 'open' and (self.counter % self.cache_interval)!=0:
            return
        if len(self) >= self.cache_size:
            first_key = next(self.data.iterkeys())
            self.data.pop(first_key)
        self.data[key] = val
Request that a key/value pair be considered for caching.
dataset/ETHPy150Open ioam/holoviews/holoviews/core/spaces.py/DynamicMap._cache