code: function findPropsWithFunctionExpression (propsNode, prop) {
        let nodes = []
        propsNode
          .filter(prop => prop.type === 'FunctionExpression')
          .map(prop => {
            return hasUsingdocument(prop)
          })
          .forEach(prop => {
            nodes = nodes.concat(prop)
          })
        return nodes
      }
docs: Finds all props that don't have a default value set
  @param {Property} propsNode - Vue component's "props" node
  @return {boolean}