text: import pytest
  
  from dicom_standard.process_ciod_module_relationship import expand_conditional_statement
  
  
  def test_expand_conditional_statement_normal_cases():
      assert expand_conditional_statement('C') == ('C', None)
      assert expand_conditional_statement('M') == ('M', None)
      assert expand_conditional_statement('U') == ('U', None)
  
  
  def test_expand_conditional_statement_with_conditional_statement():
      assert expand_conditional_statement('C - Hello') == ('C', 'Hello')
  
  
  def test_expand_conditional_statement_discards_comments_after_user_optional():
      assert expand_conditional_statement('U - Comment') == ('U', None)
  
  
  def test_expand_conditional_statement_with_conditional_statement_containing_dashes():
      assert expand_conditional_statement('C - Has - Dashes') == ('C', 'Has - Dashes')
  
  
  def test_expand_conditional_statement_raises_if_empty():
      with pytest.raises(Exception):
          expand_conditional_statement()
  