def require(self, entity_type, attribute_name=None):
if not attribute_name:<EOL><INDENT>attribute_name = entity_type<EOL><DEDENT>self.requires += [(entity_type, attribute_name)]<EOL>return self<EOL>
The intent parser should require an entity of the provided type.

Args:
    entity_type(str): an entity type
    attribute_name(str): the name of the attribute on the parsed intent. Defaults to match entity_type.

Returns:
    self: to continue modifications.