import re


def parse_case_camel_to_snake(camel):
	"""
	Convert a string from CamelCase to snake_case.

	:param str camel: The CamelCase string to convert.
	:return: The snake_case version of string.
	:rtype: str
	"""
	# requirements = re
	return re.sub('((?<=[a-z0-9])[A-Z]|(?!^)[A-Z](?=[a-z]))', r'_\1', camel).lower()