@classmethod<EOL><INDENT>def _get_operation(cls, opname):<DEDENT>
return cls.OPERATIONS.get(opname)<EOL>
Get operation from its name.
        You can override this class method to provide additional
        operations.

        :param basestring opname:
          operation name

        :return:
          binary operator if found, `None` otherwise
        :rtype: callable object