NEWBIE: opaque error message

[Eugene Leitl]

I've got this piece of code here, kindly donated as a point of
departure. 

from MMTK import *
from MMTK.Lattice import BravaisLattice

a = 4.516*Units.Ang
b = 4.516*Units.Ang
c = 7.354*Units.Ang
alpha = 90*Units.deg
beta = 90*Units.deg
gamma = 120*Units.deg

ex = Vector(1., 0., 0.)
ey = Vector(0., 1., 0.)
ez = Vector(0., 0., 1.)

# Caution: this works only for beta=90*Units.deg
a1 = a*ex
a2 = b*Rotation(ez, alpha)(ex)
a3 = c*Rotation(ey, gamma)(ex)

water = Molecule('water')
water.O.setPosition(0.3333*a1 +  0.6667*a2 + 0.0629*a3)
water.H1.setPosition(0.3333*a1 + 0.6667*a2 + 0.1989*a3)
water.H2.setPosition(0.4551*a1 + 0.9102*a2 + 0.0182*a3)

universe = InfiniteUniverse()
for point in BravaisLattice((a1, a2, a3), (3, 3, 3)):
    molecule = copy(water)
    molecule.translateTo(point)
    universe.addObject(molecule)


which produces the following error message:

Traceback (innermost last):
  File "ice.py", line 27, in ?
    molecule = copy(water)
  File "/usr/lib/python1.5/copy.py", line 76, in copy
    y = copierfunction(x)
  File "/usr/lib/python1.5/copy.py", line 110, in _copy_inst
    return x.__copy__()
  File "/usr/lib/python1.5/site-packages/MMTK/ChemicalObjects.py", line 116, in __copy__
    return copy.deepcopy(self, {id(self.parent): None})
  File "/usr/lib/python1.5/copy.py", line 151, in deepcopy
    y = copierfunction(x, memo)
  File "/usr/lib/python1.5/copy.py", line 236, in _deepcopy_inst
    state = deepcopy(state, memo)
  File "/usr/lib/python1.5/copy.py", line 151, in deepcopy
    y = copierfunction(x, memo)
  File "/usr/lib/python1.5/copy.py", line 199, in _deepcopy_dict
    y[deepcopy(key, memo)] = deepcopy(x[key], memo)
  File "/usr/lib/python1.5/copy.py", line 151, in deepcopy
    y = copierfunction(x, memo)
  File "/usr/lib/python1.5/copy.py", line 172, in _deepcopy_list
    y.append(deepcopy(a, memo))
  File "/usr/lib/python1.5/copy.py", line 151, in deepcopy
    y = copierfunction(x, memo)
  File "/usr/lib/python1.5/copy.py", line 236, in _deepcopy_inst
    state = deepcopy(state, memo)
  File "/usr/lib/python1.5/copy.py", line 151, in deepcopy
    y = copierfunction(x, memo)
  File "/usr/lib/python1.5/copy.py", line 199, in _deepcopy_dict
    y[deepcopy(key, memo)] = deepcopy(x[key], memo)
  File "/usr/lib/python1.5/copy.py", line 151, in deepcopy
    y = copierfunction(x, memo)
  File "/usr/lib/python1.5/copy.py", line 221, in _deepcopy_inst
    return x.__deepcopy__(memo)
TypeError: too many arguments; expected 1, got 2

<duh>Huh? Can somebody comment what it means?</duh>