<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def from_file(cls, paramname, filename):
 """Returns a new MultipartParam object constructed from the local file at ``filename``. ``filesize`` is determined by os.path.getsize(``filename``) ``filetype`` is determined by mimetypes.guess_type(``filename``)[0] ``filename`` is set to os.path.basename(``filename``) """


        return cls(paramname, filename=os.path.basename(filename),
                   filetype=mimetypes.guess_type(filename)[0],
                   filesize=os.path.getsize(filename),
                   fileobj=open(filename, "rb"))