def get_package_by_name(self, identifier, package_version=''):
        package_version = package_version or ''
        package_version_key = (identifier, package_version)
#         if package_version is not None and package_version.strip() == "":
#             package_version = None
        try:
            if not package_version:
                return self.packages[identifier]
            else:
                return self.package_versions[package_version_key]
        except KeyError:
            if identifier not in self.packages:
                raise MissingPackage(identifier)
            elif package_version and \
                    package_version_key not in self.package_versions:
                raise MissingPackageVersion(identifier, package_version)
dataset/ETHPy150Open VisTrails/VisTrails/vistrails/core/modules/module_registry.py/ModuleRegistry.get_package_by_name/original