code: public static BiologicalAssemblyTransformation combine(BiologicalAssemblyTransformation matrix1, BiologicalAssemblyTransformation matrix2) {
  		Matrix4d transformation = new Matrix4d(matrix1.transformation);
  		transformation.mul(matrix2.transformation);
  		BiologicalAssemblyTransformation combined = new BiologicalAssemblyTransformation();
  		combined.setTransformationMatrix(transformation);
  		return combined;
  	}
docs: Returns the combination (product) of two biological assembly transformations.
  @param matrix1
  @param matrix2
  @return combined transformation