code: def get_schema_spec(self, key):
      
      member_node = self._ast_node.member.get(key, None)
      if not member_node:
        return schema.AnySchema()
  
      s = framework.eval(member_node.member_schema, self.env(self))
      if not isinstance(s, schema.Schema):
        raise ValueError('Node %r with schema node %r should evaluate to Schema, got %r' % (member_node, member_node.member_schema, s))
      return s
docs: Return the evaluated schema expression from a subkey.