public function hasForRange($key, \DateTime $start, \DateTime $end)
    {
        return array_key_exists($this->keyForRange($key, $start, $end), $this->data);
    }
public function hasForRange($key, \DateTime $start, \DateTime $end)
    {
        return array_key_exists($this->keyForRange($key, $start, $end), $this->data);
    }
public function hasForRange ( $ key , \ DateTime $ start , \ DateTime $ end ) { return array_key_exists ( $ this -> keyForRange ( $ key , $ start , $ end ) , $ this -> data ) ; }
Determine if value exists for a given date range.

@param string $key Counter key.
@param \DateTime $start Start date.
@param \DateTime $end End date.
@return bool
Determine if value exists for a given date range .