input: Write a function to determine if the first string is a subsequence of the second string. If it is, return True; otherwise, 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", "acybx")==False
  assert is_subsequence("sing", "sting")==True
  assert is_subsequence("hat", "a great day")==False
  assert is_subsequence("abc", "abcdef")==True
output: 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)