def filter(self, value, model=None, context=None):
http = ['<STR_LIT>', '<STR_LIT>']<EOL>if all(not str(value).startswith(s) for s in http):<EOL><INDENT>value = '<STR_LIT>'.format(value)<EOL><DEDENT>return value<EOL>
Filter
Performs value filtering and returns filtered result.

:param value:           input value
:param model:           parent model being validated
:param context:         object, filtering context
:return:                filtered value