def download_structure(pdbid, save_name):
    """This class helps user to download the 3D structure of the protein and save it on a disk.

    Example:

        To Download the file    
        >>>from packman import molecule
        >>>molecule.download_structure('1prw','1prw.pdb')

    Args:
        pdbid (str)    : A Unique 4 Letter PDB ID (eg.. 1PRW) 
        save_name (str): Save name of the downloaded file (Don't forget the extension). (eg... 1PRW.pdb)
    """
    import urllib.request as ur
    response = ur.urlopen('https://files.rcsb.org/view/' + pdbid + '.pdb')
    try:
        open(save_name, 'wb').write(response.read())
    except IOError:
        None
    return True
