code: @NonNull
      public static Expression atan2(@NonNull Expression x, @NonNull Expression y) {
          if (x == null || y == null) {
              throw new IllegalArgumentException("x and y cannot be null.");
          }
          return new Expression.FunctionExpression("ATAN2()", Arrays.asList(x, y));
      }
docs: Returns the angle theta from the conversion of rectangular coordinates (x, y)
  to polar coordinates (r, theta).
  
  @param x the abscissa coordinate
  @param y the ordinate coordinate
  @return the theta component of the point (r, theta) in polar coordinates that corresponds
  to the point (x, y) in Cartesian coordinates.