Write configuration to a file-like object.

def write_to_file(self, f):
        """Write configuration to a file-like object."""
        for section, values in self._values.iteritems():
            try:
                section_name, subsection_name = section
            except ValueError:
                (section_name, ) = section
                subsection_name = None
            if subsection_name is None:
                f.write("[%s]\n" % section_name)
            else:
                f.write("[%s \"%s\"]\n" % (section_name, subsection_name))
            for key, value in values.iteritems():
                f.write("%s = %s\n" % (key, _escape_value(value)))