You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: common.rb
    path of file: ./repos/ferrocarril/spec-runner/spec/ruby/core/proc/fixtures
    
    the code of the file until where you have to start completion: module ProcSpecs
  class ToAryAsNil
    def to_ary
      nil
 
    
    def arity_check(&block)
      pn = Proc.new(&block).arity
      pr = proc(&block).arity
      lm = lambda(&block).arity

      if pn == pr and pr == lm
        return pn
      else
        return :arity_check_failed
      end