code: function ERDColumn() {
          ERDElement.apply(this, arguments);
  
          /** @member {string} */
          this.type = '';
  
          /** @member {string} */
          this.length = '';
  
          /** @member {boolean} */
          this.primaryKey = false;
  
          /** @member {boolean} */
          this.foreignKey = false;
  
          /** @member {ERDColumn} */
          this.referenceTo = null;
  
          /** @member {boolean} */
          this.nullable = false;
  
          /** @member {boolean} */
          this.unique = false;
      }
docs: ERDColumn
  @constructor