code: def _checkTable(cls, field):
          
          # Get table part
          try:
              (table, field) = field.split('.')
          except ValueError:
              table = cls._sqlTable
          # clean away white space
          table = table.strip()
          field = field.strip()
          # register table
          cls._tables[table] = None
          # and return in proper shape
          return table + '.' + field
docs: Split a field from _sqlFields into table, column.
  
          Registers the table in cls._tables, and returns a fully
          qualified table.column (default table: cls._sqlTable)