human
Solve the following python programming problem given the following code:
def dnfs(qs) : 
    '
    Converts query condition tree into a DNF of eq conds.
    Separately for each alias.

    Any negations, conditions with lookups other than __exact or __in,
    conditions on joined models and subrequests are ignored.
    __in is converted into = or = or = ...
    ' 
    SOME = object () 
    SOME_TREE = [[(None, None, SOME, True)]] 
    def negate(term) : 
        return (term [0], term [1], term [2], (not term [3])) 
def _dnf(where) : 
        '
        Constructs DNF of where tree consisting of terms in form:
            (alias, attribute, value, negation)
        meaning `alias.attribute = value`
         or `not alias.attribute = value` if negation is False

        Any conditions other then eq are dropped.
        ' 
        if isinstance (where, Lookup) : 
            if (not hasattr (where.lhs, 'target')) : 
                return SOME_TREE 
if isinstance (where.rhs, (QuerySet, Query, SQLEvaluator)) : 
                return SOME_TREE 
if isinstance (where.lhs.target, NOT_SERIALIZED_FIELDS) : 
                return SOME_TREE 
attname = where.lhs.target.attname 
            if isinstance (where, Exact) : 
                return [[(where.lhs.alias, attname, where.rhs, True)]] 
else : 
                if isinstance (where, IsNull) : 
                    return [[(where.lhs.alias, attname, None, where.rhs)]] 
else : 
                    if (isinstance (where, In) and (len (where.rhs) < LONG_DISJUNCTION)) : 
                        return [[(where.lhs.alias, attname, v, True)] for v in where.rhs] 
else : 
                        return SOME_TREE 
else : 
            if isinstance (where, EverythingNode) : 
                return [[]] 
else : 
                if isinstance (where, NothingNode) : 
                    return [] 
else : 
                    if isinstance (where, (ExtraWhere, SubqueryConstraint)) : 
                        return SOME_TREE 
else : 
                        if (len (where) == 0) : 
                            return [[]] 
else : 
                      ...

    
    

    Fix the buggy line: main_alias = dnf._meta.db_table
assistant
#Here is Python program to fix the buggy line: main_alias = dnf.

main_alias = model._meta.db_table