input: Write a function to calculate the combined length of two input strings. The function should return the length of the concatenated string.
  assert get_string_length("Hello", "World")==10
  assert get_string_length("Python", "Programming")==17
  assert get_string_length("OpenAI", "GPT")==7
  assert get_string_length("", "Empty")==5
  assert get_string_length("Te", "st")==4
output: def get_string_length(str1, str2):
      return len(str1 + str2)