code: public com.squareup.okhttp.Call getCharactersCharacterIdContractsContractIdItemsAsync(Integer characterId,
              Integer contractId, String datasource, String ifNoneMatch, String token,
              final ApiCallback<List<CharacterContractsItemsResponse>> callback) throws ApiException {
  
          com.squareup.okhttp.Call call = getCharactersCharacterIdContractsContractIdItemsValidateBeforeCall(characterId,
                  contractId, datasource, ifNoneMatch, token, callback);
          Type localVarReturnType = new TypeToken<List<CharacterContractsItemsResponse>>() {
          }.getType();
          apiClient.executeAsync(call, localVarReturnType, callback);
          return call;
      }
docs: Get contract items (asynchronously) Lists items of a particular contract
  --- This route is cached for up to 3600 seconds SSO Scope:
  esi-contracts.read_corporation_contracts.v1 SSO Scope:
  esi-contracts.read_character_contracts.v1
  
  @param characterId
  An EVE character ID (required)
  @param contractId
  ID of a contract (required)
  @param datasource
  The server name you would like data from (optional, default to
  tranquility)
  @param ifNoneMatch
  ETag from a previous request. A 304 will be returned if this
  matches the current ETag (optional)
  @param token
  Access token to use if unable to set a header (optional)
  @param callback
  The callback to be executed when the API call finishes
  @return The request call
  @throws ApiException
  If fail to process the API call, e.g. serializing the request
  body object