code: public Matrix4x3f set(Matrix3fc mat) {
          if (mat instanceof Matrix3f) {
              MemUtil.INSTANCE.copy((Matrix3f) mat, this);
          } else {
              setMatrix3fc(mat);
          }
          properties = 0;
          return this;
      }
docs: Set the left 3x3 submatrix of this {@link Matrix4x3f} to the given {@link Matrix3fc}
  and the rest to identity.
  
  @see #Matrix4x3f(Matrix3fc)
  
  @param mat
  the {@link Matrix3fc}
  @return this