code: def validate(self):
          
          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))
docs: 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