Erro Hibernate

20:43:47,578 ERROR XMLHelper:61 - Error parsing XML: XML InputStream(8) Attribute "cascade" must be declared for element type "class".
Erro ao criar a SessionFactory.org.hibernate.InvalidMappingException: Could not parse mapping document from resource br/com/plentsoft/clinica/persistencia/TratamentoConsulta.hbm.xml
 

<hibernate-mapping>
    <class name="br.com.plentsoft.clinica.modelo.Consulta">
 	<id name="codigo" column="con_codigo" type="java.lang.Integer">
           <generator class="increment"/>
        </id>
 
        <property name="codigo" column="con_valor" type="java.lang.Long" not-null="true"/>
        <property name="status" column="con_status" type="java.lang.String" length="1" not-null="true"/>
        <property name="sessao" column="con_sessao" type="java.lang.Integer" not-null="true"/>
	<property name="valor" column="con_valor" type="java.lang.Double" not-null="true"/>	

	<!-- Chaves estrangeiras -->
        <many-to-one name="medico" class="br.com.plentsoft.clinica.modelo.Medico" column="MED_CODIGO"/>
	  <many-to-one name="convenio" class="br.com.plentsoft.clinica.modelo.Convenio" column="CONV_CODIGO"/>
	  <many-to-one name="profissional" class="br.com.plentsoft.clinica.modelo.Profissional" column="PRO_CODIGO"/>
	  <many-to-one name="paciente" class="br.com.plentsoft.clinica.modelo.Paciente" column="PAC_CODIGO"/>	

		
		
      <!-- Tratamento da consulta -->
      <!-- adicionar o cascade para peristir em cascata a classe tratamento da consulta -->
      <set name="tratamento" table="TRATAMENTO_CONSULTA" lazy="false" inverse="true" cascade="all-delete-orphan"> 
         <key column="CON_CODIGO"/>
         <one-to-many class="br.com.plentsoft.clinica.modelo.TratamentoConsulta"/> 
      </set>
			
		
    </class>