def usage():
    'Print helpful, accurate usage statement to stdout.'
    print('Usage: rotate_molecule.py -f filename')
    print()
    print('    Description of command...')
    print('        [-f]    filename')
    print('    Optional parameters:')
    print('        [-o]    alternative output filename')
    print("        (default is 'rotated_' +filename)")
    print('        [-y]    rotate around the y axis')
    print('        (default is rotation around the z axis)')
    print('        [-x]    rotate around the x axis')
    print('        (default is rotation around the z axis)')
    print("        [-u]    user-defined axis of rotation '1.0,2.0,-6.2'")
    print('        (default is rotation around the z axis)')
    print('        [-a]    angle for rotation about axis ')
    print('        (default is rotation around the z axis)')
    print('        [-v]    verbose output')
Print helpful, accurate usage statement to stdout.
def usage():
    
    print('Usage: rotate_molecule.py -f filename')
    print()
    print('    Description of command...')
    print('        [-f]    filename')
    print('    Optional parameters:')
    print('        [-o]    alternative output filename')
    print("        (default is 'rotated_' +filename)")
    print('        [-y]    rotate around the y axis')
    print('        (default is rotation around the z axis)')
    print('        [-x]    rotate around the x axis')
    print('        (default is rotation around the z axis)')
    print("        [-u]    user-defined axis of rotation '1.0,2.0,-6.2'")
    print('        (default is rotation around the z axis)')
    print('        [-a]    angle for rotation about axis ')
    print('        (default is rotation around the z axis)')
    print('        [-v]    verbose output')