class Rack::Typhoeus::Middleware::ParamsDecoder

@since 0.5.4
@author Dwayne Macgowan
decode!(params)
include Rack::Typhoeus::Middleware::ParamsDecoder::Helper
require ‘rack/typhoeus/middleware/params_decoder/helper’
@example Use the helper directly. Not recommended as b/c the interface might change.
use Rack::Typhoeus::Middleware::ParamsDecoder
@example Include the middleware for Rack based applications.
require ‘typhoeus/railtie’
@example Require the railtie when using Rails.
the nested params encoded by Typhoeus.
This Rack middleware takes care of the proper deserialization of

def call(env) 

def call(env)
  req = Rack::Request.new(env)
  decode(req.params).each_pair { |k, v| update_params req, k, v }
  @app.call(env)
end

def initialize(app) 

def initialize(app)
  @app = app
end

def update_params(req, k, v)

https://github.com/rack/rack/blob/master/lib/rack/request.rb#L243
Persist params change in environment. Extracted from: 
def update_params(req, k, v)
  found = false
  if req.GET.has_key?(k)
    found = true
    req.GET[k] = v
  end
  if req.POST.has_key?(k)
    found = true
    req.POST[k] = v
  end
  unless found
    req.GET[k] = v
  end
end