code: def validate(self):
          
          if self.access_token is None:
              raise ConfigurationError('No access token provided. '
                                       'Set your access token during client initialization using: '
                                       '"basecrm.Client(access_token= <YOUR_PERSONAL_ACCESS_TOKEN>)"')
  
          if re.search(r'\s', self.access_token):
              raise ConfigurationError('Provided access token is invalid '
                                       'as it contains disallowed characters. '
                                       'Please double-check you access token.')
  
          if len(self.access_token) != 64:
              raise ConfigurationError('Provided access token is invalid '
                                       'as it has invalid length. '
                                       'Please double-check your access token.')
  
          if not self.base_url or not re.match(self.URL_REGEXP, self.base_url):
              raise ConfigurationError('Provided base url is invalid '
                                       'as it not a valid URI. '
                                       'Please make sure it incldues the schema part, '
                                       'both http and https are accepted, '
                                       'and the hierarchical part')
  
          return True
docs: Validates whether a configuration is valid.
  
          :rtype: bool
          :raises ConfigurationError: if no ``access_token`` provided.
          :raises ConfigurationError: if provided ``access_token`` is invalid - contains disallowed characters.
          :raises ConfigurationError: if provided ``access_token`` is invalid - has invalid length.
          :raises ConfigurationError: if provided ``base_url`` is invalid.