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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_asset_path(self, filename):
 """ Get the full system path of a given asset if it exists. Otherwise it throws an error. Args: filename (str) - File name of a file in /assets folder to fetch the path for. Returns: str - path to the target file. Raises: AssetNotFoundError - if asset does not exist in the asset folder. Usage:: path = WTF_ASSET_MANAGER.get_asset_path("my_asset.png") # path = /your/workspace/location/WTFProjectName/assets/my_asset.png """

        if os.path.exists(os.path.join(self._asset_path, filename)):
            return os.path.join(self._asset_path, filename)
        else:
            raise AssetNotFoundError(
                u("Cannot find asset: {0}").format(filename))