code: public SDVariable atan2(SDVariable y, SDVariable x) {
          return atan2(null, y, x);
      }
docs: Elementwise atan (arctangent, inverse tangent) operation: out = atan2(x,y).
  Similar to atan(y/x) but sigts of x and y are used to determine the location of the result
  
  @param y Input Y variable
  @param x Input X variable
  @return Output variable