class_docstr: Base class for different types of credentials
  
  Note: While subclasses can define their own `_FIELDS`, they are actually
  assumed to have particular keys by the implementation of (some)
  authenticators. `HTTPRequestsAuthenticator` and its subclasses for example,
  assume `user` and `password` to be valid keys.
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docstr: Additional house-keeping possibly to be performed in subclasses
  
  Created to avoid all the passing args/kwargs of __init__ all the time
code: def _prepare(self):
      """Additional house-keeping possibly to be performed in subclasses
  
      Created to avoid all the passing args/kwargs of __init__ all the time
      """
      # Basic checks
      for f, fattrs in self._FIELDS.items():
          unknown_attrs = set(fattrs).difference(self._KNOWN_ATTRS)
          if unknown_attrs:
              raise ValueError(
                  "Unknown attributes %s. Known are: %s"
                  % (unknown_attrs, self._KNOWN_ATTRS)
              )
  
imports: import time
  from ..support.exceptions import AccessDeniedError, CapturedException
  from ..support.keyring_ import keyring
  from ..ui import ui
  from ..utils import auto_repr
  from ..support.network import iso8601_to_epoch
  from datalad import cfg
  from datalad.config import anything2bool
  from datalad.distribution.dataset import Dataset
  from datalad.local.gitcredential import GitCredentialInterface
  from logging import getLogger
label_desc: Use image node_id 2 for calling the Credential obj's underlying member method code with example usage: obj._prepare() without return types