password_opt syntax: (1)If it's digits between 1-9, say 6, then the password will be generated randomly with the length "6". (2)If it's a string, say xxxyyyzzz, then the password is this string "xxxyyyzzz". (3)If no password_opt is given, then the password is generated randomly with the length "8". Notes! To avoid confusion between 0,1 and o,O(oh),l(lowercase L), the randomly generated password will not contain digit 0 or digit 1. </plaintext>