class Hashie::Mash

def respond_to?(method_name, include_private=false)

set in addition to normal respond_to? functionality.
Will return true if the Mash has had a key
def respond_to?(method_name, include_private=false)
  return true if key?(method_name) || method_name.to_s.slice(/[=?!_]\Z/)
  super
end