class_docstr: Simple implementation of CredentialProvider that just wraps static
  username and password.
code: def get_credentials(self):
      if self.username:
          return self.username, self.password
      return (self.password,)
  
imports: from typing import Optional, Tuple, Union
label_desc: Use image node_id 2 for calling the UsernamePasswordCredentialProvider obj's underlying member method code with example usage: obj.get_credentials() and returns: self, self,  self