@classmethod
def iter_fields(cls, model_cls):
    """ Returns an iteratorable of field names and their types. Foreign keys
        and relations must be ignored.
        
        :param model_cls: ORM model class for which column data are going to be
            returned.
        :returns: An iteratorable of tuples of type:
        
                *(field_name, field_type)*
            
            Where:
            
                - *field_name* is a name of an ORM model field.
                - *field_type* must be one of the fields of
                  :py:class:`~.column_type.ColumnType` enumeration class.
        """
    raise NotImplementedError()
