Valid

		Checks if a value is valid based on the instance's values

		Arguments:
			value {mixed} -- The value to validate

		Returns:
			bool

def valid(self, value, level=[]):
		"""Valid

		Checks if a value is valid based on the instance's values

		Arguments:
			value {mixed} -- The value to validate

		Returns:
			bool
		"""

		# Reset validation failures
		self.validation_failures = []

		# If the value is None and it's optional, we're good
		if value is None and self._optional:
			return True

		# Go through each of the nodes
		for i in range(len(self._nodes)):

			# If it's valid
			if self._nodes[i].valid(value):

				# Return OK
				return True

		# Not valid for anything
		self.validation_failures.append(('.'.join(level), 'no valid option'))
		return False