code: def parse_locustfile(file_path):
      
      if not os.path.isfile(file_path):
          color_print("file path invalid, exit.", "RED")
          sys.exit(1)
  
      file_suffix = os.path.splitext(file_path)[1]
      if file_suffix == ".py":
          locustfile_path = file_path
      elif file_suffix in ['.yaml', '.yml', '.json']:
          locustfile_path = gen_locustfile(file_path)
      else:
          # '' or other suffix
          color_print("file type should be YAML/JSON/Python, exit.", "RED")
          sys.exit(1)
  
      return locustfile_path
docs: parse testcase file and return locustfile path.
          if file_path is a Python file, assume it is a locustfile
          if file_path is a YAML/JSON file, convert it to locustfile