'Return a list of SQL statements required to remove all data from
the given database tables (without actually removing the tables
themselves) and the SQL statements required to reset the sequences
passed in `sequences`.
The `style` argument is a Style object as returned by either
color_style() or no_style() in django.core.management.color.
The `allow_cascade` argument determines whether truncation may cascade
to tables with foreign keys pointing the tables being truncated.
PostgreSQL requires a cascade even if these tables are empty.'

def sql_flush(self, style, tables, sequences, allow_cascade=False):

    raise NotImplementedError('subclasses    of    BaseDatabaseOperations    must    provide    an    sql_flush()    method')
