Parse a list of requirements specifications.
            Lines that look like "foobar==1.0" are parsed; all other lines are
            silently ignored.

            Returns a tuple of tuples, where each inner tuple is:
                (package, version)

def _parse_requirements(self, input):
        """ Parse a list of requirements specifications.
            Lines that look like "foobar==1.0" are parsed; all other lines are
            silently ignored.

            Returns a tuple of tuples, where each inner tuple is:
                (package, version) """

        results = []

        for line in input:
            (package, version) = self._parse_line(line)
            if package:
                results.append((package, version))

        return tuple(results)