def __init__(self):
    self._stack = []

    # Map from line number to number of characters it is off in indentation.
    self._start_index_offset = {}
Backends can override this to return a list of (column_name, referenced_table_name,
dataset/ETHPy150Open google/closure-linter/closure_linter/indentation.py/IndentationRules.__init__--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.4/django/db/backends/__init__.py/BaseDatabaseIntrospection.get_key_columns