How to use the pygraphviz.graphviz.agnxtattr function in pygraphviz

def iteritems(self):
        ah = None
        while 1:
            try:
                ah = gv.agnxtattr(self.ghandle, self.type, ah)
                value = gv.agxget(self.handle, ah)
                try:
                    defval = gv.agattrdefval(ah) # default value
                    if defval == value:
                        continue # don't report default
                except: # no default, gv.getattrdefval raised error
                    pass
                    # unique value for this edge
                yield (gv.agattrname(ah).decode(self.encoding),
                       value.decode(self.encoding))
            except KeyError: # gv.agxget returned KeyError, skip
                continue
            except StopIteration:  # gv.agnxtattr is done, as are we
                return

def iteritems(self):
        ah = None
        while True:
            try:
                ah = gv.agnxtattr(self.handle, self.type, ah)
                yield (gv.agattrname(ah).decode(self.encoding),
                       gv.agattrdefval(ah).decode(self.encoding))
            except KeyError: # gv.agattrdefval returned KeyError, skip
                continue
            except StopIteration:  # gv.agnxtattr is done, as are we
                return

def iteritems(self):
        ah=None
        while True:
            try:
                ah=gv.agnxtattr(self.handle,self.type,ah)
                yield (gv.agattrname(ah).decode(self.encoding),
                       gv.agattrdefval(ah).decode(self.encoding))
            except KeyError: # gv.agattrdefval returned KeyError, skip
                continue

def iteritems(self):
        ah=None
        while 1:
            try:
                ah=gv.agnxtattr(self.ghandle,self.type,ah)
                value=gv.agxget(self.handle,ah)
                try:
                    defval=gv.agattrdefval(ah) # default value
                    if defval==value:
                        continue # don't report default
                except: # no default, gv.getattrdefval raised error
                    pass
                # unique value for this edge
                yield (gv.agattrname(ah).decode(self.encoding),
                       value.decode(self.encoding))
            except KeyError: # gv.agxget returned KeyError, skip
                continue