<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def ssh_authorized_keys_lines(application_name, user=None):
 """Return contents of authorized_keys file for given application. :param application_name: Name of application eg nova-compute-something :type application_name: str :param user: The user that the ssh asserts are for. :type user: str """

    authorized_keys_list = []

    with open(authorized_keys(application_name, user)) as keys:
        for authkey_line in keys:
            if authkey_line.rstrip():
                authorized_keys_list.append(authkey_line.rstrip())
    return(authorized_keys_list)