0UT1S's

from dataclasses import dataclass
from typing import FrozenSet, Iterable, Optional, Tuple

from pip._vendor.packaging.specifiers import SpecifierSet
from pip._vendor.packaging.utils import NormalizedName
from pip._vendor.packaging.version import Version

from pip._internal.models.link import Link, links_equivalent
from pip._internal.req.req_install import InstallRequirement
from pip._internal.utils.hashes import Hashes

CandidateLookup = Tuple[Optional["Candidate"], Optional[InstallRequirement]]

def format_name(project: NormalizedName, extras: FrozenSet[NormalizedName]) -> str:
    if not extras:
        return project
    extras_expr = ",".join(sorted(extras))
    return f"{project}[{extras_expr}]"

@dataclass(frozen=True)
class Constraint:
    specifier: SpecifierSet
    hashes: Hashes
    links: FrozenSet[Link]

@classmethod
    def empty(cls) -> "Constraint":
        return Constraint(SpecifierSet(), Hashes(), frozenset())

@classmethod
    def from_ireq(cls, ireq: InstallRequirement) -> "Constraint":
        links = frozenset([ireq.link]) if ireq.link else frozenset()
        return Constraint(ireq.specifier, ireq.hashes(trust_internet=False), links)

def __bool__(self) -> bool:
        return bool(self.specifier) or bool(self.hashes) or bool(self.links)

def __and__(self, other: InstallRequirement) -> "Constraint":
        if not isinstance(other, InstallRequirement):
            return NotImplemented
        specifier = self.specifier & other.specifier
        hashes = self.hashes & other.hashes(trust_internet=False)
        links = self.links
        if other.link:
            links = links.union([other.link])
        return Constraint(specifier, hashes, links)

def is_satisfied_by(self, candidate: "Candidate") -> bool:
        # Reject if there are any mismatched URL constraints on this package.
        if self.links and not all(_match_link(link, candidate) for link in self.links):
            return False
        # We can safely always allow prereleases here since PackageFinder
        # already implements the prerelease logic, and would have filtered out
        # prerelease candidates if the user does not expect them.
        return self.specifier.contains(candidate.version, prereleases=True)

class Requirement:
    @property
    def project_name(self) -> NormalizedName:
        """The "project name" of a requirement.

This is different from ``name`` if this requirement contains extras,
        in which case ``name`` would contain the ``[...]`` part, while this
        refers to the name of the project.
        """
        raise NotImplementedError("Subclass should override")

@property
    def name(self) -> str:
        """The name identifying this requirement in the resolver.

This is different from ``project_name`` if this requirement contains
        extras, where ``project_name`` would not contain the ``[...]`` part.
        """
        raise NotImplementedError("Subclass should override")

def is_satisfied_by(self, candidate: "Candidate") -> bool:
        return False

def get_candidate_lookup(self) -> CandidateLookup:
        raise NotImplementedError("Subclass should override")

def format_for_error(self) -> str:
        raise NotImplementedError("Subclass should override")

def _match_link(link: Link, candidate: "Candidate") -> bool:
    if candidate.source_link:
        return links_equivalent(link, candidate.source_link)
    return False

class Candidate:
    @property
    def project_name(self) -> NormalizedName:
        """The "project name" of the candidate.

This is different from ``name`` if this candidate contains extras,
        in which case ``name`` would contain the ``[...]`` part, while this
        refers to the name of the project.
        """
        raise NotImplementedError("Override in subclass")

@property
    def name(self) -> str:
        """The name identifying this candidate in the resolver.

This is different from ``project_name`` if this candidate contains
        extras, where ``project_name`` would not contain the ``[...]`` part.
        """
        raise NotImplementedError("Override in subclass")

@property
    def version(self) -> Version:
        raise NotImplementedError("Override in subclass")

@property
    def is_installed(self) -> bool:
        raise NotImplementedError("Override in subclass")

@property
    def is_editable(self) -> bool:
        raise NotImplementedError("Override in subclass")

@property
    def source_link(self) -> Optional[Link]:
        raise NotImplementedError("Override in subclass")

def iter_dependencies(self, with_requires: bool) -> Iterable[Optional[Requirement]]:
        raise NotImplementedError("Override in subclass")

def get_install_requirement(self) -> Optional[InstallRequirement]:
        raise NotImplementedError("Override in subclass")

def format_for_error(self) -> str:
        raise NotImplementedError("Subclass should override")

By Order of Mr.0UT1S