plot (z-1)*(1-log(z)*(1/(1-z^-1))),(z-1)*(1-log(z)*(0.5*(1+z^-1)/(1-z^-1))),(z-1)*(1-log(z)*(0.125*(1+7*z^-1)/(1-z^-1))), z=0.9 to 1.1

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