def METHOD_NAME(self, cfn):
    """Check CloudFormation Properties"""
    matches = []
    for resourcename, resourcevalue in cfn.get_resources().items():
        if "Properties" in resourcevalue and "Type" in resourcevalue:
            resource_type = resourcevalue["Type"]
            if (
                resource_type.startswith("Custom::")
                and resource_type not in self.resourcetypes
            ):
                resource_type = "AWS::CloudFormation::CustomResource"
                matches.extend(
                    self.check_obj(
                        resourcevalue["Properties"],
                        self._get_required_attrs_specs(
                            self.resourcetypes.get(resource_type)
                        ),
                        ["Resources", resourcename, "Properties"],
                        cfn,
                    )
                )
    return matches