Convert a list of AttributeProto to a dict, with names as keys.

def _parse_attr(self, attr_proto):
        """Convert a list of AttributeProto to a dict, with names as keys."""
        attrs = {}
        for a in attr_proto:
            for f in ['f', 'i', 's']:
                if a.HasField(f):
                    attrs[a.name] = getattr(a, f)
                    # Needed for supporting python version  > 3.5
                    if isinstance(attrs[a.name], bytes):
                        attrs[a.name] = attrs[a.name].decode(encoding='utf-8')
            for f in ['floats', 'ints', 'strings']:
                if list(getattr(a, f)):
                    assert a.name not in attrs, "Only one type of attr is allowed"
                    attrs[a.name] = tuple(getattr(a, f))
            for f in ['t', 'g']:
                if a.HasField(f):
                    attrs[a.name] = getattr(a, f)
            for f in ['tensors', 'graphs']:
                if list(getattr(a, f)):
                    raise NotImplementedError("Filed {} is not supported in mxnet.".format(f))
            if a.name not in attrs:
                raise ValueError("Cannot parse attribute: \n{}\n.".format(a))
        return attrs