def _version_from_file(lines):
    """
    Given an iterable of lines from a Metadata file, return
    the value of the Version field, if present, or None otherwise.
    """
    def is_version_line(line):
        return line.lower().startswith('version:')
    version_lines = filter(is_version_line, lines)
    line = next(iter(version_lines), '')
    _, _, value = line.partition(':')
    return safe_version(value.strip()) or None

    Given an iterable of lines from a Metadata file, return
    the value of the Version field, if present, or None otherwise.
    
src/pkg_resources/__init__.py