I was trying to replace classes with position="attributes" but it dosen't work. it seems to be a bug.

This dosen't works

  <xpath expr="//div[@id='mid-header-bottom-left']" position="attributes">    <attribute name="class">"col-md-3 col-sm-2 oe_structure"</attribute>  </xpath>

This Does

  <xpath expr="//div[@id='mid-header-bottom-left']" position="attributes">    <attribute name="name">this shows</attribute>  </xpath>

So , 

• The selector is correct

• The attribute "name" can be assigned

• The attribute "class" cannot be replaced