code: def signup(self, client_id, email, password, connection, username=None,
               user_metadata=None):
          
          body = {
              'client_id': client_id,
              'email': email,
              'password': password,
              'connection': connection,
              'username': username,
              'user_metadata': user_metadata
          }
  
          return self.post(
              'https://{}/dbconnections/signup'.format(self.domain),
              data=body,
              headers={'Content-Type': 'application/json'}
          )
docs: Signup using email and password.
          
          Args:
             client_id (str): ID of the application to use.
  
             email (str): The user's email address.
  
             password (str): The user's desired password.
  
             connection (str): The name of the database connection where this user should be created.
  
             username (str, optional): The user's username, if required by the database connection.
  
             user_metadata (dict, optional): Additional key-value information to store for the user.
                      Some limitations apply, see: https://auth0.com/docs/metadata#metadata-restrictions
  
          See: https://auth0.com/docs/api/authentication#signup