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: revalue.rb
    path of file: ./repos/facets/lib/core/facets/hash
    
    the code of the file until where you have to start completion: class Hash

  # Generates a new hash where the values are the result of the passed in
  # block.  The block ta
    
  def revalue(val_map=nil, &block)
    raise ArgumentError, "argument or block, not both" if val_map && block

    if !(val_map or block)
      raise ArgumentError, "must provide Hash arguments or a block"
      #block = lambda{|v| v.to_s}
    end