from pathlib import Path


def get_genbank_paths(folder):
    """Generate a collection of paths to GenBank files in a specified folder."""
    if not Path(folder).is_dir():
        raise ValueError("Expected valid folder")
    valid_extensions = (".gb", ".gbk", ".genbank")
    return [
        file for file in Path(folder).iterdir() if str(file).endswith(valid_extensions)
    ]