input: Write a python function to compare two strings and determine their length and equality.
  assert string_compare("Hello World", "Bye World") == "str1 is longer"
  assert string_compare("Hi", "Hello") == "str2 is longer"
  assert string_compare("test", "test") == "strings are equal"
  assert string_compare("apple", "apples") == "str2 is longer"
  assert string_compare("banana", "banana") == "strings are equal"
output: def string_compare(str1, str2):
      if len(str1) > len(str2):
          return "str1 is longer"
      elif len(str1) < len(str2):
          return "str2 is longer"
      else:
          return "strings are equal"