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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_hash(self, ireq, ireq_hashes=None):
 """ Retrieve hashes for a specific ``InstallRequirement`` instance. :param ireq: An ``InstallRequirement`` to retrieve hashes for :type ireq: :class:`~pip_shims.InstallRequirement` :return: A set of hashes. :rtype: Set """


        # We _ALWAYS MUST PRIORITIZE_ the inclusion of hashes from local sources
        # PLEASE *DO NOT MODIFY THIS* TO CHECK WHETHER AN IREQ ALREADY HAS A HASH
        # RESOLVED. The resolver will pull hashes from PyPI and only from PyPI.
        # The entire purpose of this approach is to include missing hashes.
        # This fixes a race condition in resolution for missing dependency caches
        # see pypa/pipenv#3289
        if not self._should_include_hash(ireq):
            return set()
        elif self._should_include_hash(ireq) and (
            not ireq_hashes or ireq.link.scheme == "file"
        ):
            if not ireq_hashes:
                ireq_hashes = set()
            new_hashes = self.resolver.repository._hash_cache.get_hash(ireq.link)
            ireq_hashes = add_to_set(ireq_hashes, new_hashes)
        else:
            ireq_hashes = set(ireq_hashes)
        # The _ONLY CASE_ where we flat out set the value is if it isn't present
        # It's a set, so otherwise we *always* need to do a union update
        if ireq not in self.hashes:
            return ireq_hashes
        else:
            return self.hashes[ireq] | ireq_hashes