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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 envars_to_markdown(envars, title = "Environment"):
    '''generate a markdown list of a list of environment variable tuples

       Parameters
       ==========
       title: A title for the section (defaults to "Environment"
       envars: a list of tuples for the environment, e.g.:

            [('TERM', 'xterm-256color'),
             ('SHELL', '/bin/bash'),
             ('USER', 'vanessa'),
             ('LD_LIBRARY_PATH', ':/usr/local/pulse')]

    '''
    markdown = ''
    if envars not in [None, '', []]:
        markdown += '\n## %s\n' % title
        for envar in envars:
            markdown += ' - **%s**: %s\n' %(envar[0], envar[1])
    return markdown