text: #ifndef UTIL_INCLUDES
  #define UTIL_INCLUDES
  #include <memory>
  #include <string>
  #include <unordered_map>
  #include <unordered_set>
  #include <vector>
  
  #include "absl/types/optional.h"
  #include "absl/memory/memory.h"
  #include "util/logging.h"
  #include "util/strings.h"
  #include "util/files.h"
  
  #include "coln/api.h"
  #include "coln/map.h"
  #include "coln/seq.h"
  #include "coln/set.h"
  
  #include "google/protobuf/map.h"
  #include "google/protobuf/stubs/common.h"
  #include "google/protobuf/stubs/logging.h"
  #include "google/protobuf/stubs/status_macros.h"
  #include "google/protobuf/stubs/statusor.h"
  #include "google/protobuf/testing/file.h"
  #include "google/protobuf/text_format.h"
  
  namespace vectorbook {
  // std using statements.
  using std::endl;
  using std::pair;
  using std::function;
  using std::string;
  using std::unique_ptr;
  using std::shared_ptr;
  using std::unordered_map;
  using std::unordered_set;
  using std::vector;
  
  // optional.
  using absl::nullopt;
  using absl::optional;
  
  // protobuf using statements.
  using google::protobuf::TextFormat;
  using google::protobuf::RepeatedPtrField;
  
  time_t CurrentTimeInfo();
  
  } // namespace vectorbook
  #endif /* UTIL_INCLUDES */
  