docs: def command_schema(self, name=None):
          '''
          Prints current database schema (according sqlalchemy database model)::
  
              ./manage.py sqla:schema [name]
          '''
          meta_name = table_name = None
          if name:
              if isinstance(self.metadata, MetaData):
                  table_name = name
              elif '.' in name:
                  meta_name, table_name = name.split('.', 1)
              else:
                  meta_name = name
  
          def _print_metadata_schema(metadata):
              if table_name is None:
                  for table in metadata.sorted_tables:
                      print(self._schema(table))
              else:
                  try:
                      table = metadata.tables[table_name]
                  except KeyError:
                      sys.exit('Table {} is not found'.format(name))
                  print(self._schema(table))
  
          if isinstance(self.metadata, MetaData):
              _print_metadata_schema(self.metadata)
          else:
              for current_meta_name, metadata in self.metadata.items():
                  if meta_name not in (current_meta_name, None):
                      continue
                  _print_metadata_schema(metadata)