input: Write a function to determine if the first string is a subsequence of the second string. If the first string is a subsequence, return True, otherwise return False. If either string is empty, return False.
  def is_subsequence(str1, str2):
      if not str1:
          return False
      if 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)
  
  assert is_subsequence("abc", "qaxbcy")==True
  assert is_subsequence("axc", "ahbgdc")==False
  assert is_subsequence("abc", "abcde")==True
  assert is_subsequence("abc", "")==False
  assert is_subsequence("", "abcde")==False
output: def is_subsequence(str1, str2):
      if not str1:
          return False
      if 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)