class Aws::Rest::Request::Body

def modeled_body?

either with payload trait or normal members.
operation is modeled for body when it is modeled for a payload 
def modeled_body?
  return true if @rules[:payload]
  @rules.shape.members.each do |member|
    _name, shape = member
    return true if shape.location.nil?
  end
  false
end