ESP8266HueEmulator: I can't compile the code

Please advise for any mistake I did. I can’t get through this. Thank you so much

WARNING: Category '' in library Digole is not valid. Setting to 'Uncategorized'
In file included from /Volumes/XRAIDDrive/GMMTV/Download/ESP8266HueEmulator-master/ESP8266HueEmulator/ESP8266HueEmulator.ino:19:0:
/Users/thom/Documents/Arduino/libraries/aJson-master-2/aJSON.h:92:6: error: conflicting return type specified for 'virtual int aJsonStream::flush()'
  int flush();
      ^
In file included from /Users/thom/Library/Arduino15/packages/esp8266/hardware/esp8266/2.4.0/cores/esp8266/Stream.h:26:0,
                 from /Users/thom/Library/Arduino15/packages/esp8266/hardware/esp8266/2.4.0/cores/esp8266/HardwareSerial.h:31,
                 from /Users/thom/Library/Arduino15/packages/esp8266/hardware/esp8266/2.4.0/cores/esp8266/Arduino.h:246,
                 from sketch/ESP8266HueEmulator.ino.cpp:1:
/Users/thom/Library/Arduino15/packages/esp8266/hardware/esp8266/2.4.0/cores/esp8266/Print.h:93:22: error:   overriding 'virtual void Print::flush()'
         virtual void flush() { /* Empty implementation for backward compatibility */ }
                      ^
exit status 1
Error compiling for board WeMos D1 mini Pro.