How to use the pbr.packaging.parse_requirements function in pbr

def setup_hook(config):
    """Filter config parsed from a setup.cfg to inject our defaults."""
    metadata = config['metadata']
    metadata['version'] = packaging.get_version(metadata['name'],
                                                metadata.get('version', None))
    metadata['requires_dist'] = "\n".join(packaging.parse_requirements())
    config['metadata'] = metadata

    config['global'] = config.get('global', dict())
    config['global']['commands'] = config['global'].get('commands', "") + """
pbr.packaging.LocalSDist
"""
    if packaging.have_sphinx():
        config['global']['commands'] = config['global']['commands'] + """
pbr.packaging.LocalBuildDoc
pbr.packaging.LocalBuildLatex
"""

    pbr_config = config.get('pbr', dict())
    use_egg = packaging.get_boolean_option(
        pbr_config, 'use-egg', 'PBR_USE_EGG')
    # We always want non-egg install unless explicitly requested

# install_requires are treated as a special case of extras, before
    # being put back in the expected place
    #
    # fred =
    #     foo:marker
    #     bar
    # -> {'fred': ['bar'], 'fred:marker':['foo']}

    if 'extras' in config:
        requirement_pattern = '(?P[^:]*):?(?P[^#]*?)(?:\s*#.*)?$'
        extras = config['extras']
        # Add contents of test-requirements, if any, into an extra named
        # 'test' if one does not already exist.
        if 'test' not in extras:
            from pbr import packaging
            extras['test'] = "\n".join(packaging.parse_requirements(
                packaging.TEST_REQUIREMENTS_FILES)).replace(';', ':')

        for extra in extras:
            extra_requirements = []
            requirements = split_multiline(extras[extra])
            for requirement in requirements:
                m = re.match(requirement_pattern, requirement)
                extras_value = m.group('package').strip()
                env_marker = m.group('env_marker')
                extra_requirements.append((extras_value,env_marker))
            all_requirements[extra] = extra_requirements

    # Transform the full list of requirements into:
    # - install_requires, for those that have no extra and no
    #   env_marker
    # - named extras, for those with an extra name (which may include

def hook(self):
        self.config['version'] = packaging.get_version(
            self.config['name'], self.config.get('version', None))
        packaging.append_text_list(
            self.config, 'requires_dist',
            packaging.parse_requirements())

# install_requires are treated as a special case of extras, before
    # being put back in the expected place
    #
    # fred =
    #     foo:marker
    #     bar
    # -> {'fred': ['bar'], 'fred:marker':['foo']}

    if 'extras' in config:
        requirement_pattern = '(?P[^:]*):?(?P[^#]*?)(?:\s*#.*)?$'
        extras = config['extras']
        # Add contents of test-requirements, if any, into an extra named
        # 'test' if one does not already exist.
        if 'test' not in extras:
            from pbr import packaging
            extras['test'] = "\n".join(packaging.parse_requirements(
                packaging.TEST_REQUIREMENTS_FILES)).replace(';', ':')

        for extra in extras:
            extra_requirements = []
            requirements = split_multiline(extras[extra])
            for requirement in requirements:
                m = re.match(requirement_pattern, requirement)
                extras_value = m.group('package').strip()
                env_marker = m.group('env_marker')
                extra_requirements.append((extras_value,env_marker))
            all_requirements[extra] = extra_requirements

    # Transform the full list of requirements into:
    # - install_requires, for those that have no extra and no
    #   env_marker
    # - named extras, for those with an extra name (which may include

# being put back in the expected place
    #
    # fred =
    #     foo:marker
    #     bar
    # -> {'fred': ['bar'], 'fred:marker':['foo']}

    if 'extras' in config:
        requirement_pattern = (
            r'(?P[^:]*):?(?P[^#]*?)(?:\s*#.*)?$')
        extras = config['extras']
        # Add contents of test-requirements, if any, into an extra named
        # 'test' if one does not already exist.
        if 'test' not in extras:
            from pbr import packaging
            extras['test'] = "\n".join(packaging.parse_requirements(
                packaging.TEST_REQUIREMENTS_FILES)).replace(';', ':')

        for extra in extras:
            extra_requirements = []
            requirements = split_multiline(extras[extra])
            for requirement in requirements:
                m = re.match(requirement_pattern, requirement)
                extras_value = m.group('package').strip()
                env_marker = m.group('env_marker')
                extra_requirements.append((extras_value, env_marker))
            all_requirements[extra] = extra_requirements

    # Transform the full list of requirements into:
    # - install_requires, for those that have no extra and no
    #   env_marker
    # - named extras, for those with an extra name (which may include

def hook(self):
        self.config['include_package_data'] = 'True'
        packaging.append_text_list(
            self.config, 'dependency_links',
            packaging.parse_dependency_links())
        packaging.append_text_list(
            self.config, 'tests_require',
            packaging.parse_requirements(
                packaging.TEST_REQUIREMENTS_FILES,
                strip_markers=True))