import re


def format_string(prop_string):
    """
        Formats a property string to remove spaces and go from CamelCase to pep8
        from: http://stackoverflow.com/questions/1175208/elegant-python-function-to-convert-camelcase-to-camel-case
    """
    if prop_string is None:
        return ''
    st_r = re.sub('(.)([A-Z][a-z]+)', r'\1_\2', prop_string)
    st_r = st_r.replace(' ', '')
    return re.sub('([a-z0-9])([A-Z])', r'\1_\2', st_r).lower()