Returns :prop:intervals as a numpy array, caches

            -> :class:numpy.array

def array(self):
        """ Returns :prop:intervals as a numpy array, caches

            -> :class:numpy.array
        """
        if self._intervals_len:
            if self._array_len != self._intervals_len:
                if not self._array_len:
                    self._array = np.array(self.intervals) \
                        if hasattr(np, 'array') else self.intervals
                else:
                    self._array = np.concatenate((
                        self._array, self.intervals), axis=0) \
                        if hasattr(np, 'concatenate') else \
                        (self._array + self.intervals)
                self._array_len += len(self.intervals)
                self.intervals = []
            return self._array
        return []