code: def displayEmptyInputWarningBox(display=True, parent=None):
      
      if sys.version_info[0] >= 3:
          from tkinter.messagebox import showwarning
      else:
          from tkMessageBox import showwarning
  
      if display:
          msg = 'No valid input files found! '+\
          'Please check the value for the "input" parameter.'
          showwarning(parent=parent,message=msg, title="No valid inputs!")
      return "yes"
docs: Displays a warning box for the 'input' parameter.