class ActiveRecord::ConnectionAdapters::PostgreSQL::OID::Hstore

def serialize(value)
  if value.is_a?(::Hash)
    value.map { |k, v| "#{escape_hstore(k)}=>#{escape_hstore(v)}" }.join(", ")
  elsif value.respond_to?(:to_unsafe_h)
    serialize(value.to_unsafe_h)
  else
    value
  end
end