def coerce(cls, version_string, partial=False):
        """Coerce an arbitrary version string into a semver-compatible one.

        The rule is:
        - If not enough components, fill minor/patch with zeroes; unless
          partial=True
        - If more than 3 dot-separated components, extra components are "build"
          data. If some "build" data already appeared, append it to the
          extra components

        Examples:
            >>> Version.coerce('0.1')
            Version(0, 1, 0)
            >>> Version.coerce('0.1.2.3')
            Version(0, 1, 2, (), ('3',))
            >>> Version.coerce('0.1.2.3+4')
            Version(0, 1, 2, (), ('3', '4'))
            >>> Version.coerce('0.1+2-3+4_5')
            Version(0, 1, 0, (), ('2-3', '4-5'))
        """
        base_re = re.compile(r'^\d+(?:\.\d+(?:\.\d+)?)?')

        match = base_re.match(version_string)
        if not match:
            raise ValueError(
                "Version string lacks a numerical component: %r"
                % version_string
            )

        version = version_string[:match.end()]
        if not partial:
            # We need a not-partial version.
            while version.count('.') < 2:
                version += '.0'

        # Strip leading zeros in components
        # Version is of the form nn, nn.pp or nn.pp.qq
        version = '.'.join(
            # If the part was '0', we end up with an empty string.
            part.lstrip('0') or '0'
            for part in version.split('.')
        )

        if match.end() == len(version_string):
            return Version(version, partial=partial)

        rest = version_string[match.end():]

        # Cleanup the 'rest'
        rest = re.sub(r'[^a-zA-Z0-9+.-]', '-', rest)

        if rest[0] == '+':
            # A 'build' component
            prerelease = ''
            build = rest[1:]
        elif rest[0] == '.':
            # An extra version component, probably 'build'
            prerelease = ''
            build = rest[1:]
        elif rest[0] == '-':
            rest = rest[1:]
            if '+' in rest:
                prerelease, build = rest.split('+', 1)
            else:
                prerelease, build = rest, ''
        elif '+' in rest:
            prerelease, build = rest.split('+', 1)
        else:
            prerelease, build = rest, ''

        build = build.replace('+', '.')

        if prerelease:
            version = '%s-%s' % (version, prerelease)
        if build:
            version = '%s+%s' % (version, build)

        return cls(version, partial=partial)
Coerce an arbitrary version string into a semver-compatible one.

        The rule is:
        - If not enough components, fill minor/patch with zeroes; unless
          partial=True
        - If more than 3 dot-separated components, extra components are "build"
          data. If some "build" data already appeared, append it to the
          extra components

        Examples:
            >>> Version.coerce('0.1')
            Version(0, 1, 0)
            >>> Version.coerce('0.1.2.3')
            Version(0, 1, 2, (), ('3',))
            >>> Version.coerce('0.1.2.3+4')
            Version(0, 1, 2, (), ('3', '4'))
            >>> Version.coerce('0.1+2-3+4_5')
            Version(0, 1, 0, (), ('2-3', '4-5'))
        
src/semantic_version.py