docs: def show_schema(self, tables=None):
          """Print schema information."""
          tables = tables if tables else self.tables
          for t in tables:
              self._printer('\t{0}'.format(t))
              for col in self.get_schema(t, True):
                  self._printer('\t\t{0:30} {1:15} {2:10} {3:10} {4:10} {5:10}'.format(*col))