quickFlipCurves

import maya.mel as mel
import maya.cmds as cmds

'''
Quickly scale your selected keys or entire animation curves by -1, if you have keys selected in the graphEditor, they will all be scaled.
If no keys are selected, the currently highlighted channels in the channelbox will be flipped
'''

gChannelBoxName = mel.eval('$temp=$gChannelBoxName')
selection = cmds.ls(sl=True)
chList = cmds.channelBox(gChannelBoxName,
                                  query=True,
                                  selectedMainAttributes=True)
cmds.scaleKey(includeUpperBound=False, valueScale=-1, valuePivot=-1, animation='keysOrObjects', attribute=chList)