def parse_requirements(self, network_configuration=None):
        # type: (Optional[NetworkConfiguration]) -> Iterable[ParsedRequirement]
        parsed_requirements = []  # type: List[ParsedRequirement]
        if self.requirements:
            parsed_requirements.extend(parse_requirement_strings(self.requirements))
        if self.requirement_files:
            fetcher = URLFetcher(network_configuration=network_configuration)
            for requirement_file in self.requirement_files:
                parsed_requirements.extend(
                    requirement_or_constraint
                    for requirement_or_constraint in parse_requirement_file(
                        requirement_file, is_constraints=False, fetcher=fetcher
                    )
                    if not isinstance(requirement_or_constraint, Constraint)
                )
        return parsed_requirements