Need urgent help

my project support ftp .Now we want to add sftp functionality also to it. Actually in the project files are collected from different server by not using the get function but first cstring() of python is used to store the data in memory and then then binary is retrived using retrbinary and then it is stored using storbinary() of ftplib.so,i have to do sftp using paramiko in the the same manner. But paramiko does not support retrbinary nor storebinary function so please help me out what to do.
Please .................................