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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def validate_swagger_schema(schema_dir, resource_listing):
 """Validate the structure of Swagger schemas against the spec. **Valid only for Swagger v1.2 spec** Note: It is possible that resource_listing is not present in the schema_dir. The path is passed in the call so that ssv can fetch the api-declaration files from the path. :param resource_listing: Swagger Spec v1.2 resource listing :type resource_listing: dict :param schema_dir: A path to Swagger spec directory :type schema_dir: string :raises: :py:class:`swagger_spec_validator.SwaggerValidationError` """

    schema_filepath = os.path.join(schema_dir, API_DOCS_FILENAME)
    swagger_spec_validator.validator12.validate_spec(
        resource_listing,
        urlparse.urljoin('file:', pathname2url(os.path.abspath(schema_filepath))),
    )