title: Gamma function with complex input in Tensorflow
body: <p>I am trying to compute the gamma function in Tensorflow. The argument in the function is a sum of a float that comes from the tensor and an imaginary part. Normally, I could just exponentiate the <code>tf.math.lgamma</code> function, however, it does not accept complex numbers. Is there any workaround that could solve this issue?</p>