code: def _addColumn(cat, col):
      
      # 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
docs: 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