input: Write a function to evaluate a string expression and handle syntax errors.
  assert evaluate_string("3 + 5") == 8
  assert evaluate_string("10 / 2") == 5.0
  assert evaluate_string("5 + ") == "Syntax Error"
output: def evaluate_string(expression):
      try:
          return eval(expression)
      except SyntaxError:
          return "Syntax Error"