code: def _requirement_filter_by_marker(req):
      # type: (pkg_resources.Requirement) -> bool
      
      if hasattr(req, 'marker') and req.marker:
          marker_env = {
              'python_version': '.'.join(map(str, sys.version_info[:2])),
              'sys_platform': sys.platform
          }
          if not req.marker.evaluate(environment=marker_env):
              return False
      return True
docs: Check if the requirement is satisfied by the marker.
  
      This function checks for a given Requirement whether its environment marker
      is satisfied on the current platform. Currently only the python version and
      system platform are checked.