quantum-core/lib/select.js
function isEntity (d) {
  return isText(d.type) && Array.isArray(d.params) && Array.isArray(d.content)
}
function isEntity (d) {
  return isText(d.type) && Array.isArray(d.params) && Array.isArray(d.content)
}
function isEntity ( d ) { return isText ( d . type ) && Array . isArray ( d . params ) && Array . isArray ( d . content ) }
duck type check for an entity
duck type check for an entity