def _addColumn(cat, col):
    """
    This function adds a metadata column to the acatalog.
    :cat: a catalog object
    :col: a column id as string
    :returns: a boolean as True if the element has been added and
        False otherwise
    """
    # First check if the metadata column already exists
    if col not in cat.schema():
        try:
            cat.addColumn(col)
            logger.info('Column %s added to %s.' % (col, cat.id))
            return True
        except:
            logger.error(
                'Catalog column %s error while adding to %s.' % (col, cat.id))
    return False