lib/agent.js
function validateId(id) {
    if (id && id.trim() && /^[a-zA-Z0-9_]+$/.test(id)) {
      if (agency.isIdInUse(id)) {
        err.name = 'DuplicateIdError';
        err.message = 'duplication (use a different id)'; 
        return err;
      } else {
        return id;
      }
    } else {
      err.name = 'ValidateIdError';
      err.message = 'failed id validation (please use alphanumeric characters and underscore)'; 
      return err;
    }
  }
function validateId(id) {
    if (id && id.trim() && /^[a-zA-Z0-9_]+$/.test(id)) {
      if (agency.isIdInUse(id)) {
        err.name = 'DuplicateIdError';
        err.message = 'duplication (use a different id)'; 
        return err;
      } else {
        return id;
      }
    } else {
      err.name = 'ValidateIdError';
      err.message = 'failed id validation (please use alphanumeric characters and underscore)'; 
      return err;
    }
  }
validates the agent's id according to the validity of the symbols used and the possibility of duplication inside the same agency