code: def constraint_from_parent_conflicts(self):
          
          # ensure that we satisfy the parent dependencies of this dep
          from pipenv.vendor.packaging.specifiers import Specifier
          parent_dependencies = set()
          has_mismatch = False
          can_use_original = True
          for p in self.parent_deps:
              # updated dependencies should be satisfied since they were resolved already
              if p.is_updated:
                  continue
              # parents with no requirements can't conflict
              if not p.requirements:
                  continue
              needed = p.requirements.get("dependencies", [])
              entry_ref = p.get_dependency(self.name)
              required = entry_ref.get("required_version", "*")
              required = self.clean_specifier(required)
              parent_requires = self.make_requirement(self.name, required)
              parent_dependencies.add("{0} => {1} ({2})".format(p.name, self.name, required))
              if not parent_requires.requirement.specifier.contains(self.original_version):
                  can_use_original = False
              if not parent_requires.requirement.specifier.contains(self.updated_version):
                  has_mismatch = True
          if has_mismatch and not can_use_original:
              from pipenv.exceptions import DependencyConflict
              msg = (
                  "Cannot resolve {0} ({1}) due to conflicting parent dependencies: "
                  "\n\t{2}".format(
                      self.name, self.updated_version, "\n\t".join(parent_dependencies)
                  )
              )
              raise DependencyConflict(msg)
          elif can_use_original:
              return self.lockfile_entry.as_ireq()
          return self.entry.as_ireq()
docs: Given a resolved entry with multiple parent dependencies with different
          constraints, searches for the resolution that satisfies all of the parent
          constraints.
  
          :return: A new **InstallRequirement** satisfying all parent constraints
          :raises: :exc:`~pipenv.exceptions.DependencyConflict` if resolution is impossible