Create a parser by defining which input files it will read from.

        Input:
            directory - str, directory to read from
            files - str, list of files from which to search.

def generate_from_directory(cls, directory):
        """Create a parser by defining which input files it will read from.

        Input:
            directory - str, directory to read from
            files - str, list of files from which to search.
            """
        files = [os.path.join(directory, f) for f in os.listdir(directory)
                 if os.path.isfile(os.path.join(directory, f))]
        return cls(files)