<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def validate(self):
 """ Check that the Xmrs is well-formed. The Xmrs is analyzed and a list of problems is compiled. If any problems exist, an :exc:`XmrsError` is raised with the list joined as the error message. A well-formed Xmrs has the following properties: * All predications have an intrinsic variable * Every intrinsic variable belongs one predication and maybe one quantifier * Every predication has no more than one quantifier * All predications have a label * The graph of predications form a net (i.e. are connected). Connectivity can be established with variable arguments, QEQs, or label-equality. * The lo-handle for each QEQ must exist as the label of a predication """

        errors = []
        ivs, bvs = {}, {}
        _vars = self._vars
        _hcons = self._hcons
        labels = defaultdict(set)
        # ep_args = {}
        for ep in self.eps():
            nid, lbl, args, is_q = (
                ep.nodeid, ep.label, ep.args, ep.is_quantifier()
            )
            if lbl is None:
                errors.append('EP ({}) is missing a label.'.format(nid))
            labels[lbl].add(nid)
            iv = args.get(IVARG_ROLE)
            if iv is None:
                errors.append('EP {nid} is missing an intrinsic variable.'
                              .format(nid))
            if is_q:
                if iv in bvs:
                    errors.append('{} is the bound variable for more than '
                                  'one quantifier.'.format(iv))
                bvs[iv] = nid
            else:
                if iv in ivs:
                    errors.append('{} is the intrinsic variable for more '
                                  'than one EP.'.format(iv))
                ivs[iv] = nid
            # ep_args[nid] = args
        for hc in _hcons.values():
            if hc[2] not in labels:
                errors.append('Lo variable of HCONS ({} {} {}) is not the '
                              'label of any EP.'.format(*hc))
        if not self.is_connected():
            errors.append('Xmrs structure is not connected.')
        if errors:
            raise XmrsError('\n'.join(errors))