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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 run_pip_install(upgrade=0):
 """ Installs the requirement.txt file on the given server. Usage:: fab <server> run_pip_install fab <server> run_pip_install:upgrade=1 :param upgrade: If set to 1, the command will be executed with the ``--upgrade`` flag. """

    command = 'pip install -r {0}'.format(
        settings.FAB_SETTING('SERVER_REQUIREMENTS_PATH'))
    if upgrade:
        command += ' --upgrade'
    run_workon(command)