code: public Map<String, List<CloudVolumeStorage>> getCloudVolumes(Map<String, String> instanceToAccountMap) {
          Map<String, List<CloudVolumeStorage>> returnMap = new HashMap<>();
          DescribeVolumesResult volumeResult = ec2Client.describeVolumes();
          for (Volume v : volumeResult.getVolumes()) {
              CloudVolumeStorage object = new CloudVolumeStorage();
              for (VolumeAttachment va : v.getAttachments()) {
                  object.getAttachInstances().add(va.getInstanceId());
              }
              String account = NO_ACCOUNT;
              //Get any instance id if any and get corresponding account number
              if (!CollectionUtils.isEmpty(object.getAttachInstances()) &&
                      !StringUtils.isEmpty(instanceToAccountMap.get(object.getAttachInstances().get(0)))) {
                  account = instanceToAccountMap.get(object.getAttachInstances().get(0));
              }
              object.setAccountNumber(account);
              object.setZone(v.getAvailabilityZone());
              object.setAccountNumber(account);
              object.setCreationDate(v.getCreateTime().getTime());
              object.setEncrypted(v.isEncrypted());
              object.setSize(v.getSize());
              object.setStatus(v.getState());
              object.setType(v.getVolumeType());
              object.setVolumeId(v.getVolumeId());
              List<Tag> tags = v.getTags();
              if (!CollectionUtils.isEmpty(tags)) {
                  for (Tag tag : tags) {
                      NameValue nv = new NameValue(tag.getKey(), tag.getValue());
                      object.getTags().add(nv);
                  }
              }
              if (CollectionUtils.isEmpty(returnMap.get(object.getAccountNumber()))) {
                  List<CloudVolumeStorage> temp = new ArrayList<>();
                  temp.add(object);
                  returnMap.put(account, temp);
              } else {
                  returnMap.get(account).add(object);
              }
          }
          return returnMap;
      }
docs: Returns a map of account number of list of volumes associated with the account
  
  @param instanceToAccountMap
  @return Map of account number and a list of Volumes