code: def from_master_password(cls, password, network=BitcoinMainNet):
          
          password = ensure_bytes(password)
          key = sha256(password).hexdigest()
          return cls.from_hex_key(key, network)
docs: Generate a new key from a master password.
  
          This password is hashed via a single round of sha256 and is highly
          breakable, but it's the standard brainwallet approach.
  
          See `PrivateKey.from_master_password_slow` for a slightly more
          secure generation method (which will still be subject to a rainbow
          table attack :\)