input: Write a function to convert the given temperature from Celsius to Fahrenheit. If the given temperature is empty or invalid, return -1.
  assert celsius_to_fahrenheit(0)==32
  assert celsius_to_fahrenheit(100)==212
  assert celsius_to_fahrenheit(-40)==-40
  assert celsius_to_fahrenheit(37)==98.6
  assert celsius_to_fahrenheit(None)==-1
output: def celsius_to_fahrenheit(celsius):
      if celsius is None or not isinstance(celsius, (int, float)):
          return -1
      return (celsius * 9/5) + 32