input: Write a function to determine if the first string is a subsequence of the second. A subsequence is a string that can be derived from another string by deleting some characters without changing the order of the remaining characters. If the first string is a subsequence of the second, return True; otherwise, return False. If either string is empty, return False.
  
  def is_subsequence(str1, str2):
      i = 0
      j = 0
  
      while(i < len(str1) and j < len(str2)):
          if str1[i] == str2[j]:
              i += 1
          j += 1
  
      return i == len(str1)
  
  assert is_subsequence("abc", "qaxbcy") == True
  assert is_subsequence("abc", "qaxbcy") == True
  assert is_subsequence("abc", "qaxyzc") == False
  assert is_subsequence("", "qaxbcy") == False
  assert is_subsequence("abc", "") == False
output: def is_subsequence(str1, str2):
      if not str1 or not str2:
          return False
      i = 0
      j = 0
  
      while i < len(str1) and j < len(str2):
          if str1[i] == str2[j]:
              i += 1
          j += 1
  
      return i == len(str1)