code: function validateColumns(columns) {
    if (!columns) {
      return;
    }
  
    // check IDs
    var ids = {};
    columns.forEach(function (column, i) {
      var id = column.id;
  
      if (!ids[id]) {
        ids[id] = [i];
      } else {
        ids[id].push(i);
      }
    });
    Object.keys(ids).forEach(function (id) {
      if (ids[id].length > 1) {
        console.warn('Column ID \'' + id + '\' used in multiple columns ' + ids[id].join(', '), ids[id].map(function (index) {
          return columns[index];
        }));
      }
    });
  }
docs: Checks an array of column definitions to see if there are any issues.
  Checks if
  
  - multiple columns have the same ID
  
  Typically only used in development.
  
  @param {Object[]} columns The column definitions for the whole table
  @returns {void}