The "official" string representation of an object. If at all possible, this should look like a valid R expression that could be used to recreate an object wit the same value (given an appropriate environment). This description is copied from the python documentation.
Examples
EMAIL <- new_class(class_name = "EMAIL")
email <- EMAIL$instantiate
register_method(EMAIL, ..init.. = function(address) self$address = address)
patrick <- email('patrick@test.com')
repr(patrick)
#> [1] "email(\"patrick@test.com\")"