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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 put_headers_in_environ(headers, environ):
 """Given a list of headers, put them into environ based on PEP-333. This converts headers to uppercase, prefixes them with 'HTTP_', and converts dashes to underscores before adding them to the environ dict. Args: headers: A list of (header, value) tuples. The HTTP headers to add to the environment. environ: An environ dict for the request as defined in PEP-333. """

  for key, value in headers:
    environ['HTTP_%s' % key.upper().replace('-', '_')] = value