code: public function blobExists($containerName = '', $blobName = '', $snapshotId = null)
      {
          Assertion::notEmpty($containerName, 'Container name is not specified');
          self::assertValidContainerName($containerName);
          Assertion::notEmpty($blobName, 'Blob name is not specified.');
  
          try {
              $this->getBlobInstance($containerName, $blobName, $snapshotId);
          } catch (BlobException $e) {
              return false;
          }
  
          return true;
      }
docs: Check if a blob exists
  
  @param string $containerName Container name
  @param string $blobName      Blob name
  @param string $snapshotId    Snapshot identifier
  @return boolean