class RSpec::Core::Metadata

def relevant_line_numbers(metadata=self)

metadata[:example_group] is not always a kind of GroupMetadataHash.
TODO - make this a method on metadata - the problem is 
def relevant_line_numbers(metadata=self)
  [metadata[:line_number]] + (metadata[:example_group] ? relevant_line_numbers(metadata[:example_group]) : [])
end