class Concurrent::MultipleAssignmentError

(such as an ‘IVar`) after its final state has been set.
Raised when an attempt is made to modify an immutable object

def initialize(message = nil, inspection_data = nil) 

def initialize(message = nil, inspection_data = nil)
  @inspection_data = inspection_data
  super message
end

def inspect 

def inspect
  format '%s %s>', super[0..-2], @inspection_data.inspect
end