docs: def up(self, migration_id=None, fake=False):
          """Executes migrations."""
          if not self.check_directory():
              return
  
          for migration in self.get_migrations_to_up(migration_id):
              logger.info('Executing migration: %s' % migration.filename)
  
              migration_module = self.load_migration_file(migration.filename)
              if not fake:
                  if hasattr(migration_module, 'up'):
                      migration_module.up(self.db)
                  else:
                      logger.error('No up method on migration %s' % migration.filename)
  
              record = migration.as_dict()
              record['date'] = datetime.utcnow()
              self.collection.insert(record)