Created starter files for the project.

venv/Lib/site-packages/pip/_internal/resolution/resolvelib/base.py

@@ -0,0 +1,82 @@
+from pip._vendor.packaging.utils import canonicalize_name
+
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
+
+if MYPY_CHECK_RUNNING:
+    from typing import FrozenSet, Iterable, Optional, Tuple
+
+    from pip._vendor.packaging.version import _BaseVersion
+
+    from pip._internal.models.link import Link
+    from pip._internal.req.req_install import InstallRequirement
+
+    CandidateLookup = Tuple[
+        Optional["Candidate"],
+        Optional[InstallRequirement],
+    ]
+
+
+def format_name(project, extras):
+    # type: (str, FrozenSet[str]) -> str
+    if not extras:
+        return project
+    canonical_extras = sorted(canonicalize_name(e) for e in extras)
+    return "{}[{}]".format(project, ",".join(canonical_extras))
+
+
+class Requirement(object):
+    @property
+    def name(self):
+        # type: () -> str
+        raise NotImplementedError("Subclass should override")
+
+    def is_satisfied_by(self, candidate):
+        # type: (Candidate) -> bool
+        return False
+
+    def get_candidate_lookup(self):
+        # type: () -> CandidateLookup
+        raise NotImplementedError("Subclass should override")
+
+    def format_for_error(self):
+        # type: () -> str
+        raise NotImplementedError("Subclass should override")
+
+
+class Candidate(object):
+    @property
+    def name(self):
+        # type: () -> str
+        raise NotImplementedError("Override in subclass")
+
+    @property
+    def version(self):
+        # type: () -> _BaseVersion
+        raise NotImplementedError("Override in subclass")
+
+    @property
+    def is_installed(self):
+        # type: () -> bool
+        raise NotImplementedError("Override in subclass")
+
+    @property
+    def is_editable(self):
+        # type: () -> bool
+        raise NotImplementedError("Override in subclass")
+
+    @property
+    def source_link(self):
+        # type: () -> Optional[Link]
+        raise NotImplementedError("Override in subclass")
+
+    def iter_dependencies(self, with_requires):
+        # type: (bool) -> Iterable[Optional[Requirement]]
+        raise NotImplementedError("Override in subclass")
+
+    def get_install_requirement(self):
+        # type: () -> Optional[InstallRequirement]
+        raise NotImplementedError("Override in subclass")
+
+    def format_for_error(self):
+        # type: () -> str
+        raise NotImplementedError("Subclass should override")