# Buggy code
def expand(segments, recurse=True, parse_depth=0, verbosity=0, dialect=None):
    segs = tuple()
    for stmt in segments:
        try:
            if not stmt.is_expandable:
                logging.info(
                    "[PD:{0}] Skipping expansion of {1}...".format(parse_depth, stmt)
                )
                segs += (stmt,)
                continue
        except Exception as err:
            # raise ValueError("{0} has no attribute `is_expandable`. This segment appears poorly constructed.".format(stmt))
            logging.error(
                "{0} has no attribute `is_expandable`. This segment appears poorly constructed.".format(
                    stmt
                )
            )
            raise err
        if not hasattr(stmt, "parse"):
            raise ValueError(
                "{0} has no method `parse`. This segment appears poorly constructed.".format(
                    stmt
                )
            )
        parse_depth_msg = "Parse Depth {0}. Expanding: {1}: {2!r}".format(
            parse_depth, stmt.__class__.__name__, curtail_string(stmt.raw, length=40)
        )
        verbosity_logger(frame_msg(parse_depth_msg), verbosity=verbosity)
        res = stmt.parse(
            recurse=recurse,
            parse_depth=parse_depth,
            verbosity=verbosity,
            dialect=dialect,
        )
        if isinstance(res, BaseSegment):
            segs += (res,)
        else:
            # We might get back an iterable of segments
            segs += tuple(res)
    # Basic Validation
    check_still_complete(segments, segs, tuple())
    return segs


# Traceback (TypeError)
Traceback (most recent call last):
File "/home/user/sql/.venv/bin/sqlfluff", line 11, in <module>
load_entry_point('sqlfluff==0.1.3', 'console_scripts', 'sqlfluff')()
File "/home/user/sql/.venv/lib/python3.7/site-packages/click/core.py", line 764, in __call__
return self.main(*args, **kwargs)
File "/home/user/sql/.venv/lib/python3.7/site-packages/click/core.py", line 717, in main
rv = self.invoke(ctx)
File "/home/user/sql/.venv/lib/python3.7/site-packages/click/core.py", line 1137, in invoke
return _process_result(sub_ctx.command.invoke(sub_ctx))
File "/home/user/sql/.venv/lib/python3.7/site-packages/click/core.py", line 956, in invoke
return ctx.invoke(self.callback, **ctx.params)
File "/home/user/sql/.venv/lib/python3.7/site-packages/click/core.py", line 555, in invoke
return callback(*args, **kwargs)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/cli/commands.py", line 85, in lint
result = lnt.lint_paths(paths, verbosity=verbose)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/linter.py", line 324, in lint_paths
result.add(self.lint_path(path, verbosity=verbosity, fix=fix))
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/linter.py", line 312, in lint_path
linted_path.add(self.lint_file(f, fname=fname, verbosity=verbosity, fix=fix))
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/linter.py", line 212, in lint_file
parsed, vs, time_dict = self.parse_file(f=f, fname=fname, verbosity=verbosity)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/linter.py", line 193, in parse_file
parsed = fs.parse(recurse=recurse, verbosity=verbosity, dialect=self.dialect)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 228, in parse
verbosity=verbosity, dialect=dialect)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 394, in expand
res = stmt.parse(recurse=recurse, parse_depth=parse_depth, verbosity=verbosity, dialect=dialect)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 228, in parse
verbosity=verbosity, dialect=dialect)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 394, in expand
res = stmt.parse(recurse=recurse, parse_depth=parse_depth, verbosity=verbosity, dialect=dialect)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 228, in parse
verbosity=verbosity, dialect=dialect)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 394, in expand
res = stmt.parse(recurse=recurse, parse_depth=parse_depth, verbosity=verbosity, dialect=dialect)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 228, in parse
verbosity=verbosity, dialect=dialect)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 394, in expand
res = stmt.parse(recurse=recurse, parse_depth=parse_depth, verbosity=verbosity, dialect=dialect)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 186, in parse
dialect=dialect, match_segment=self.__class__.__name__)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 70, in _match
verbosity=verbosity, dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 273, in match
verbosity=verbosity, dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 70, in _match
verbosity=verbosity, dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 485, in match
match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 70, in _match
verbosity=verbosity, dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 273, in match
verbosity=verbosity, dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 70, in _match
verbosity=verbosity, dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 236, in match
dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 361, in _match
verbosity=verbosity, dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/segments_base.py", line 320, in match
dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 70, in _match
verbosity=verbosity, dialect=dialect, match_segment=match_segment)
File "/home/user/sql/.venv/lib/python3.7/site-packages/sqlfluff/parser/grammar.py", line 586, in match
segment=segments[start_bracket_idx])
TypeError: tuple indices must be integers or slices, not NoneType

# Fixed code
def expand(segments, parse_context):
    segs = tuple()
    for stmt in segments:
        try:
            if not stmt.is_expandable:
                logging.info(
                    "[PD:{0}] Skipping expansion of {1}...".format(
                        parse_context.parse_depth, stmt
                    )
                )
                segs += (stmt,)
                continue
        except Exception as err:
            # raise ValueError("{0} has no attribute `is_expandable`. This segment appears poorly constructed.".format(stmt))
            logging.error(
                "{0} has no attribute `is_expandable`. This segment appears poorly constructed.".format(
                    stmt
                )
            )
            raise err
        if not hasattr(stmt, "parse"):
            raise ValueError(
                "{0} has no method `parse`. This segment appears poorly constructed.".format(
                    stmt
                )
            )
        parse_depth_msg = "Parse Depth {0}. Expanding: {1}: {2!r}".format(
            parse_context.parse_depth,
            stmt.__class__.__name__,
            curtail_string(stmt.raw, length=40),
        )
        verbosity_logger(frame_msg(parse_depth_msg), verbosity=parse_context.verbosity)
        res = stmt.parse(parse_context=parse_context)
        if isinstance(res, BaseSegment):
            segs += (res,)
        else:
            # We might get back an iterable of segments
            segs += tuple(res)
    # Basic Validation
    check_still_complete(segments, segs, tuple())
    return segs