\[ \int \frac {1}{\tanh ^{-1}(\tanh (a+b x))^{3/2}} \, dx \]
Optimal antiderivative \[ -\frac {2}{b \sqrt {\arctanh \left (\tanh \left (b x +a \right )\right )}} \]
command
integrate(1/atanh(tanh(b*x+a))**(3/2),x)
Sympy 1.10.1 under Python 3.10.4 output
\[ \begin {cases} - \frac {2}{b \sqrt {\operatorname {atanh}{\left (\tanh {\left (a + b x \right )} \right )}}} & \text {for}\: b \neq 0 \\\frac {x}{\operatorname {atanh}^{\frac {3}{2}}{\left (\tanh {\left (a \right )} \right )}} & \text {otherwise} \end {cases} \]
Sympy 1.8 under Python 3.8.8 output
\[ \text {Exception raised: TypeError} \]________________________________________________________________________________________