:return: Load configuration from the environment and return a configured instance

def fromenv() -> 'VaultAuth12Factor':
        """
        :return: Load configuration from the environment and return a configured instance
        """
        i = None  # type: VaultAuth12Factor
        if os.getenv("VAULT_TOKEN", None):
            i = VaultAuth12Factor.token(os.getenv("VAULT_TOKEN"))
        elif os.getenv("VAULT_APPID", None) and os.getenv("VAULT_USERID", None):
            i = VaultAuth12Factor.app_id(os.getenv("VAULT_APPID"), os.getenv("VAULT_USERID"))
        elif os.getenv("VAULT_ROLEID", None) and os.getenv("VAULT_SECRETID", None):
            i = VaultAuth12Factor.approle(os.getenv("VAULT_ROLEID"), os.getenv("VAULT_SECRETID"))
        elif os.getenv("VAULT_SSLCERT", None) and os.getenv("VAULT_SSLKEY", None):
            i = VaultAuth12Factor.ssl_client_cert(os.getenv("VAULT_SSLCERT"), os.getenv("VAULT_SSLKEY"))

        if i:
            e = os.getenv("VAULT_UNWRAP", "False")
            if e.lower() in ["true", "1", "yes"]:
                i.unwrap_response = True
            return i

        raise VaultCredentialProviderException("Unable to configure Vault authentication from the environment")