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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 get_artifact_filename(self, package_name, artifact_name):
 """ Similar to pkg_resources.resource_filename, however this works with the information cached in this registry instance, and arguments are not quite the same. Arguments: package_name The name of the package to get the artifact from artifact_name The exact name of the artifact. Returns the path of where the artifact should be if it has been declared, otherwise None. """


        project_name = self.packages.normalize(package_name)
        return self.records.get((project_name, artifact_name))