human
Complete the below
def _mask_nc(eq, name=None):

    ''''Return ``eq`` with non-commutative objects replaced with Dummy
    symbols. A dictionary that can be used to restore the original
    values is returned: if it is None, the expression is noncommutative
    and cannot be made commutative. The third value returned is a list
    of any non-commutative symbols that appear in the returned equation.
    ``name``, if given, is the name that will be used with numered Dummy
    variables that will replace the non-commutative objects and is mainly
    used for doctesting purposes.
    Notes
    All non-commutative objects other than Symbols are replaced with
    a non-commutative Symbol. Identical objects will be identified
    by identical symbols.
    If there is only 1 non-commutative object in an expression it will
    be replaced with a commutative symbol. Otherwise, the non-commutative
    entities are retained and the calling routine should handle
    replacements in this case since some care must be taken to keep
    track of the ordering of symbols when they occur within Muls.
    Examples
    >>> from sympy.physics.secondquant import Commutator, NO, F, Fd
    >>> from sympy import symbols, Mul
    >>> from sympy.core.exprtools import _mask_nc
    >>> from sympy.abc import x, y
    >>> A, B, C = symbols(\'A,B,C\', commutative=False)
    One nc-symbol:
    >>> _mask_nc(A**2 - x**2, \'d\')
    (_d0**2 - x**2, {_d0: A}, [])
    Multiple nc-symbols:
    >>> _mask_nc(A**2 - B**2, \'d\')
    (A**2 - B**2, None, [A, B])
    An nc-object with nc-symbols but no others outside of it:
    >>> _mask_nc(1 + x*Commutator(A, B), \'d\')
    (_d0*x + 1, {_d0: Commutator(A, B)}, [])
    >>> _mask_nc(NO(Fd(x)*F(y)), \'d\')
    (_d0, {_d0: NO(CreateFermion(x)*AnnihilateFermion(y))}, [])
    Multiple nc-objects:
    >>> eq = x*Commutator(A, B) + x*Commutator(A, C)*Commutator(A, B)
    >>> _mask_nc(eq, \'d\')
    (x*_d0 + x*_d1*_d0, {_d0: Commutator(A, B), _d1: Commutator(A, C)}, [_d0, _d1])
    Multiple nc-objects and nc-symbols:
    >>> eq = A*Commutator(A, B) + B*Commutator(A,...'''
 What is a the Python code you requested?
assistant
#Here is the Python code you requested.
    name = (name or 'mask')
    def numbered_names():
        i = 0
        while True:
            (yield (name + str(i)))
            i += 1
    names = numbered_names()
    def Dummy(*args, **kwargs):
        from sympy import Dummy
        return Dummy(next(names), *args, **kwargs)
    expr = eq
    if expr.is_commutative:
        return (eq, {}, [])
    rep = []
    nc_obj = set()
    nc_syms = set()
    pot = preorder_traversal(expr, keys=default_sort_key)
    for (i, a) in enumerate(pot):
        if any(((a == r[0]) for r in rep)):
            pot.skip()
        elif (not a.is_commutative):
            if a.is_Symbol:
                nc_syms.add(a)
            elif (not (a.is_Add or a.is_Mul or a.is_Pow)):
                if all((s.is_commutative for s in a.free_symbols)):
                    rep.append((a, Dummy()))
                else:
                    nc_obj.add(a)
                pot.skip()
    if ((len(nc_obj) == 1) and (not nc_syms)):
        rep.append((nc_obj.pop(), Dummy()))
    elif ((len(nc_syms) == 1) and (not nc_obj)):
        rep.append((nc_syms.pop(), Dummy()))
    nc_obj = sorted(nc_obj, key=default_sort_key)
    for n in nc_obj:
        nc = Dummy(commutative=False)
        rep.append((n, nc))
        nc_syms.add(nc)
    expr = expr.subs(rep)
    nc_syms = list(nc_syms)
    nc_syms.sort(key=default_sort_key)
    return (expr, ({v: k for (k, v) in rep} or None), nc_syms)