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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 __find_executables(path):
 """Used by find_graphviz path - single directory as a string If any of the executables are found, it will return a dictionary containing the program names as keys and their paths as values. Otherwise returns None """

    
    success = False
    progs = {'dot': '', 'twopi': '', 'neato': '', 'circo': '', 'fdp': '', 'sfdp': ''}
    
    was_quoted = False
    path = path.strip()
    if path.startswith('"') and path.endswith('"'):
        path = path[1:-1]
        was_quoted =  True
    
    if os.path.isdir(path) : 
    
        for prg in progs.iterkeys():
    
            if progs[prg]:
                continue
               
            if os.path.exists( os.path.join(path, prg) ):
                
                if was_quoted:
                    progs[prg] = '"' + os.path.join(path, prg) + '"'
                else:
                    progs[prg] = os.path.join(path, prg)
                    
                success = True
               
            elif os.path.exists( os.path.join(path, prg + '.exe') ):

                if was_quoted:
                    progs[prg] = '"' + os.path.join(path, prg + '.exe') + '"'
                else:
                    progs[prg] = os.path.join(path, prg + '.exe')
                    
                success = True
    
    if success:
    
        return progs
        
    else:
    
        return None