<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_cgi_parameter_file(form: cgi.FieldStorage, key: str) -> Optional[bytes]: """ Extracts a file's contents from a "file" input in a CGI form, or None if no such file was uploaded. """

    (filename, filecontents) = get_cgi_parameter_filename_and_file(form, key)
    return filecontents