text: 
  export default Mixin(superclass => class ExpressionTemplates extends superclass {
  
    expr_template (node, separator) {
      let str = ''
  
      if (_.isArray(node)) {
        let a = []
        for (let n of node) {
          a.push(this.expr(n))
        }
        str = a.join(separator || '')
      }
  
      else {
        let d = node && node.data || {}
        let t = node ? this.template(node, d) : { tmpl: 'undefined', dat: {} }
        str = _.template(t.tmpl)(t.dat)
      }
  
      return str
    }
  
  })
  