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: mutable.rb
    path of file: ./repos/arachni/lib/arachni/element/json/capabilities
    
    the code of the file until where you have to start completion: =begin
    Copyright 2010-2022 Ecsypno <http://www.ecsypno.com>

    This file is part of the
    
    def each_mutation( payload, options = {}, &block )
        return if self.inputs.empty?

        if !valid_input_data?( payload )
            print_debug_level_2 "Payload not supported by #{self}: #{payload.inspect}"
            return
        end