docs: def check_if_exists(self):
          """Find an installed distribution that satisfies or conflicts
          with this requirement, and set self.satisfied_by or
          self.conflicts_with appropriately."""
          if self.req is None:
              return False
          try:
              self.satisfied_by = pkg_resources.get_distribution(self.req)
          except pkg_resources.DistributionNotFound:
              return False
          except pkg_resources.VersionConflict:
              self.conflicts_with = pkg_resources.get_distribution(self.req.project_name)
          return True