input: 
  def is_subsequence(str1, str2):
      """
      Check if the first string is a subsequence of the second string.
      >>> is_subsequence("abc", "qaxbcy")
      True
      >>> is_subsequence("abc", "qaxybzc")
      True
      >>> is_subsequence("abc", "axybzc")
      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)
  
output:     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)