def certify_required(value, required=False):
<EOL>if not isinstance(required, bool):<EOL><INDENT>raise CertifierParamError(<EOL>'<STR_LIT>',<EOL>required,<EOL>)<EOL><DEDENT>if value is None:<EOL><INDENT>if required:<EOL><INDENT>raise CertifierValueError(<EOL>message="<STR_LIT>",<EOL>)<EOL><DEDENT>return True<EOL><DEDENT>
Certify that a value is present if required.

:param object value:
    The value that is to be certified.
:param bool required:
    Is the value required?
:raises CertifierValueError:
    Required value is `None`.