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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def merged_pex(cls, path, pex_info, interpreter, pexes, interpeter_constraints=None):
 """Yields a pex builder at path with the given pexes already merged. :rtype: :class:`pex.pex_builder.PEXBuilder` """

    pex_paths = [pex.path() for pex in pexes if pex]
    if pex_paths:
      pex_info = pex_info.copy()
      pex_info.merge_pex_path(':'.join(pex_paths))

    with safe_concurrent_creation(path) as safe_path:
      builder = PEXBuilder(safe_path, interpreter, pex_info=pex_info)
      if interpeter_constraints:
        for constraint in interpeter_constraints:
          builder.add_interpreter_constraint(constraint)
      yield builder