def _format_filter(filters, and_props=[]):
        """
        Transform filters to a comprehensive WQL `WHERE` clause.

        Builds filter from a filter list.
        - filters: expects a list of dicts, typically:
                - [{'Property': value},...] or
                - [{'Property': (comparison_op, value)},...]

                NOTE: If we just provide a value we defailt to '=' comparison operator.
                Otherwise, specify the operator in a tuple as above: (comp_op, value)
                If we detect a wildcard character ('%') we will override the operator
                to use LIKE
        """

        def build_where_clause(fltr):
            f = fltr.pop()
            wql = ""
            while f:
                prop, value = f.popitem()

                if isinstance(value, tuple):
                    oper = value[0]
                    value = value[1]
                elif isinstance(value, string_types) and '%' in value:
                    oper = 'LIKE'
                else:
                    oper = '='

                if isinstance(value, list):
                    if not len(value):
                        continue

                    internal_filter = map(
                        lambda x: (prop, x)
                        if isinstance(x, tuple)
                        else (prop, ('LIKE', x))
                        if '%' in x
                        else (prop, (oper, x)),
                        value,
                    )

                    bool_op = ' OR '
                    for p in and_props:
                        if p.lower() in prop.lower():
                            bool_op = ' AND '
                            break

                    clause = bool_op.join(
                        [
                            '{0} {1} \'{2}\''.format(k, v[0], v[1])
                            if isinstance(v, tuple)
                            else '{0} = \'{1}\''.format(k, v)
                            for k, v in internal_filter
                        ]
                    )

                    if bool_op.strip() == 'OR':
                        wql += "( {clause} )".format(clause=clause)
                    else:
                        wql += "{clause}".format(clause=clause)

                else:
                    wql += "{property} {cmp} '{constant}'".format(property=prop, cmp=oper, constant=value)
                if f:
                    wql += " AND "

            # empty list skipped
            if wql.endswith(" AND "):
                wql = wql[:-5]

            if len(fltr) == 0:
                return "( {clause} )".format(clause=wql)

            return "( {clause} ) OR {more}".format(clause=wql, more=build_where_clause(fltr))

        if not filters:
            return ""

        return " WHERE {clause}".format(clause=build_where_clause(filters))