input: from typing import List
  
  def fix_syntax_errors(code: str) -> str:
      """Detect and fix Python syntax errors in a given code snippet.
      Use a try-except block to handle NameError for variables that are not defined.
      >>> fix_syntax_errors("def test ():\n    x = 5\n    y = 3\n    z")
      "def test():\n    x = 5\n    y = 3\n    try:\n        z\n    except NameError:\n        print(\"NameError: Name 'z' is not defined\")"
      """
output:     try:
          exec(code)
      except NameError as e:
          error_message = str(e)
          if "is not defined" in error_message:
              variable_name = error_message.split("'")[1]
              code = code.replace(variable_name, f"try:\n        {variable_name}\n    except NameError:\n        print(\"NameError: Name '{variable_name}' is not defined\")")
      return code