def MeSigmaIDeriv(self, u): 
        # TODO: only works for diagonal tensors. getEdgeInnerProductDeriv, invMat=True should be implemented in SimPEG

        dMeSigmaI_dI = -self.MeSigmaI**2
        dMe_dsig = self.mesh.getEdgeInnerProductDeriv(self.curModel.sigma)(u)
        dsig_dm = self.curModel.sigmaDeriv
        return dMeSigmaI_dI * ( dMe_dsig * ( dsig_dm))
        # return self.mesh.getEdgeInnerProductDeriv(self.curModel.sigma, invMat=True)(u)
This method is called when an image is set in a channel.
dataset/ETHPy150Open simpeg/simpeg/SimPEG/EM/Base.py/BaseEMProblem.MeSigmaIDeriv--crossover with--dataset/ETHPy150Open ejeschke/ginga/ginga/misc/plugins/Contents.py/Contents.redo