code: def to_string(crs):
      """Turn a parameter mapping into a more conventional PROJ.4 string.
  
      Mapping keys are tested against the ``all_proj_keys`` list. Values of
      ``True`` are omitted, leaving the key bare: {'no_defs': True} -> "+no_defs"
      and items where the value is otherwise not a str, int, or float are
      omitted.
      """
      items = []
      for k, v in sorted(
          filter(
              lambda x: x[0] in all_proj_keys
              and x[1] is not False
              and (
                  isinstance(x[1], (bool, int, float))
                  or isinstance(x[1], str)
              ),
              crs.items(),
          )
      ):
          items.append(
              "+"
              + "=".join(
                  map(
                      str,
                      filter(
                          lambda y: (y or y == 0) and y is not True,
                          (k, v),
                      ),
                  )
              )
          )
      return " ".join(items)
  
label_desc: Use image node_id 1 for calling a global function with example usage: to_string(crs) and returns: str