def _output_file(self, frame):
if self.buff:<EOL><INDENT>return self.buff<EOL><DEDENT>elif self.multifile:<EOL><INDENT>return self.file_root + "<STR_LIT>" % frame + self.file_ext<EOL><DEDENT>else:<EOL><INDENT>return self.filename<EOL><DEDENT>
If filename was used output a filename, along with multifile
numbered filenames will be used.

If buff was specified it is returned.

:return: Output buff or filename.