code: function(str) {
      var startsWith = !_.isNull(str.match(rOpsHeadRe))
      return startsWith & cons.isLegalSentence(str)
    }
docs: Check if the string is a RETURN|DELETE|DETACH DELETE operation string and is legal.
  @private
  @param  {string}  str RETURN sentence.
  @return {Boolean}