Assert\Assertion::float PHP Method

    public static function float($value, $message = null, $propertyPath = null)
    {
        if (!is_float($value)) {
            $message = sprintf($message ?: 'Value "%s" is not a float.', static::stringify($value));
            throw static::createException($value, $message, static::INVALID_FLOAT, $propertyPath);
        }
        return true;
    }

 public function customMetric($metricName, $value)
 {
     Assertion::string($metricName);
     Assertion::notBlank($metricName);
     Assertion::float($value);
     return $this->handle('newrelic_custom_metric', [$metricName, $value]);
 }