code: func ParseRuleFromBody(module *Module, body Body) (*Rule, error) {
  
  	if len(body) != 1 {
  		return nil, fmt.Errorf("multiple expressions cannot be used for rule head")
  	}
  
  	return ParseRuleFromExpr(module, body[0])
  }
docs: // ParseRuleFromBody returns a rule if the body can be interpreted as a rule
  // definition. Otherwise, an error is returned.