# File lib/backports/1.8.7/array/shift.rb, line 6
    def shift_with_optional_argument(n = Backports::Undefined)
      return shift_without_optional_argument if n == Backports::Undefined
      n = Backports.coerce_to_int(n)
      raise ArgumentError, "negative array size" if n < 0
      slice!(0, n)
    end