How to use the chempy.cpv.get_angle function in chempy

def pdbBox(line):
        ''' Parses a gro box line and returns a pdb CRYST1 line '''
        from math import degrees
        from chempy.cpv import length, get_angle

        v = [10*float(i) for i in line.split()] + 6*[0] # Padding for rectangular boxes
        v1, v2, v3 = (v[0], v[3], v[4]), (v[5], v[1], v[6]), (v[7], v[8], v[2])

        a = length(v1)
        b = length(v2)
        c = length(v3)

        alpha = degrees(get_angle(v2, v3))
        beta = degrees(get_angle(v1, v3))
        gamma = degrees(get_angle(v1, v2))

        return _pdbBoxLine % (a, b, c, alpha, beta, gamma)

def pdbBox(line):
        ''' Parses a gro box line and returns a pdb CRYST1 line '''
        from math import degrees
        from chempy.cpv import length, get_angle

        v = [10*float(i) for i in line.split()] + 6*[0] # Padding for rectangular boxes
        v1, v2, v3 = (v[0], v[3], v[4]), (v[5], v[1], v[6]), (v[7], v[8], v[2])

        a = length(v1)
        b = length(v2)
        c = length(v3)

        alpha = degrees(get_angle(v2, v3))
        beta = degrees(get_angle(v1, v3))
        gamma = degrees(get_angle(v1, v2))

        return _pdbBoxLine % (a, b, c, alpha, beta, gamma)

def pdbBox(line):
        ''' Parses a gro box line and returns a pdb CRYST1 line '''
        from math import degrees
        from chempy.cpv import length, get_angle

        v = [10*float(i) for i in line.split()] + 6*[0] # Padding for rectangular boxes
        v1, v2, v3 = (v[0], v[3], v[4]), (v[5], v[1], v[6]), (v[7], v[8], v[2])

        a = length(v1)
        b = length(v2)
        c = length(v3)

        alpha = degrees(get_angle(v2, v3))
        beta = degrees(get_angle(v1, v3))
        gamma = degrees(get_angle(v1, v2))

        return _pdbBoxLine % (a, b, c, alpha, beta, gamma)

visualize, quiet, sigma_cutoff = int(visualize), int(quiet), float(sigma_cutoff)
    stored.x = dict()
    cmd.iterate_state(STATE, '(%s) and name C+O' % (selection),
                      'stored.x.setdefault(chain + resi, dict())[name] = x,y,z')
    vec_list = []
    count = 0
    for x in stored.x.values():
        if 'C' in x and 'O' in x:
            vec_list.append(cpv.sub(x['O'], x['C']))
            count += 1
    if count == 0:
        print('warning: count == 0')
        raise CmdException
    vec = _vec_sum(vec_list)
    if count > 2 and sigma_cutoff > 0:
        angle_list = [cpv.get_angle(vec, x) for x in vec_list]
        angle_mu, angle_sigma = _mean_and_std(angle_list)
        vec_list = [vec_list[i] for i in range(len(vec_list))
                    if abs(angle_list[i] - angle_mu) < angle_sigma * sigma_cutoff]
        if not quiet:
            print('Dropping %d outlier(s)' % (len(angle_list) - len(vec_list)))
        vec = _vec_sum(vec_list)
    vec = cpv.normalize(vec)
    return _common_orientation(selection, vec, visualize, quiet)

visualize, quiet, sigma_cutoff = int(visualize), int(quiet), float(sigma_cutoff)
    stored.x = dict()
    cmd.iterate_state(-1, '(%s) and name C+O' % (selection),
            'stored.x.setdefault(chain + resi, dict())[name] = x,y,z')
    vec_list = []
    count = 0
    for x in stored.x.itervalues():
        if 'C' in x and 'O' in x:
            vec_list.append(cpv.sub(x['O'], x['C']))
            count += 1
    if count == 0:
        print 'warning: count == 0'
        raise CmdException
    vec = _vec_sum(vec_list)
    if count > 2 and sigma_cutoff > 0:
        angle_list = [cpv.get_angle(vec, x) for x in vec_list]
        angle_mu, angle_sigma = _mean_and_std(angle_list)
        vec_list = [vec_list[i] for i in range(len(vec_list))
                if abs(angle_list[i] - angle_mu) < angle_sigma * sigma_cutoff]
        if not quiet:
            print 'Dropping %d outlier(s)' % (len(angle_list) - len(vec_list))
        vec = _vec_sum(vec_list)
    vec = cpv.normalize(vec)
    return _common_orientation(selection, vec, visualize, quiet)

state1, state2 = int(state1), int(state2)
    visualize, quiet = int(visualize), int(quiet)

    try:
        orientation = globals()[methods_sc[str(method)]]
    except KeyError:
        print('no such method:', method)
        raise CmdException

    if not int(quiet):
        print(' Using method:', orientation.__name__)

    cen1, dir1 = orientation(selection1, state1, visualize, quiet=1)
    cen2, dir2 = orientation(selection2, state2, visualize, quiet=1)

    angle = cpv.get_angle(dir1, dir2)
    angle = math.degrees(angle)

    if not quiet:
        print(' Angle: %.2f deg' % (angle))

    if visualize:
        # measurement object for angle
        center = cpv.scale(cpv.add(cen1, cen2), 0.5)
        tmp = get_unused_name('_')
        for pos in [center,
                cpv.add(center, cpv.scale(dir1, 5.0)),
                cpv.add(center, cpv.scale(dir2, 5.0))]:
            cmd.pseudoatom(tmp, pos=list(pos), state=1)
        name = get_unused_name('angle')
        cmd.angle(name, *[(tmp, i) for i in [2,1,3]])
        cmd.delete(tmp)

'0': helix_orientation,
        '1': helix_orientation_hbond,
        '2': loop_orientation,
        '3': cafit_orientation,
    }
    methods.update((x.__name__, x) for x in methods.values())
    try:
        orientation = methods[str(method)]
    except KeyError:
        print 'no such method:', method
        raise CmdException
    if not quiet:
        print 'Using method:', orientation.__name__
    cen1, dir1 = orientation(selection1, visualize, quiet=1)
    cen2, dir2 = orientation(selection2, visualize, quiet=1)
    angle = cpv.get_angle(dir1, dir2)
    angle_deg = math.degrees(angle)
    if not quiet:
        print 'Angle: %.2f deg' % (angle_deg)
    if visualize:
        cmd.zoom('(%s) or (%s)' % (selection1, selection2), buffer=2)
    return angle_deg