code: def _compile_time_check():
      """Return True if compile-time support for Hexagon is present, otherwise
      error string.
  
      Designed for use as a the ``compile_time_check`` argument to
      `tvm.testing.Feature`.
      """
      if (
          tvm.testing.utils._cmake_flag_enabled("USE_LLVM")
          and tvm.target.codegen.llvm_version_major() < 7
      ):
          return "Hexagon requires LLVM 7 or later"
  
      if "HEXAGON_TOOLCHAIN" not in os.environ:
          return f"Missing environment variable {HEXAGON_TOOLCHAIN}."
  
      return True
  
imports: import os
  import tvm
label_desc: Use image node_id 1 for calling a global function with example usage: _compile_time_check() and returns: True, str, str, HEXAGON_TOOLCHAIN, str