module Aws::Endpoints::Templater

def extract_value(key, parameters, assigns)
  if assigns.key?(key)
    assigns[key]
  elsif parameters.class.singleton_class::PARAM_MAP.key?(key)
    member_name = parameters.class.singleton_class::PARAM_MAP[key]
    parameters[member_name]
  else
    raise "Templatable value not found: #{key}"
  end
end