def _update(self, value):
if not value:<EOL><INDENT>value = self._coerce()<EOL><DEDENT>elif isinstance(value, six.string_types):<EOL><INDENT>value = self._coerce(value.split(self._sep))<EOL><DEDENT>else:<EOL><INDENT>value = self._coerce(value)<EOL><DEDENT>self._value = value<EOL>
Alert method used when the variable's value in an ``Environment``
instance has been altered.

:param value: The new value to set the value to.