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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 add(modname, features, required_version, installed_version=None,
 optional=False):

 """Add Spyder dependency"""

    global DEPENDENCIES
    for dependency in DEPENDENCIES:
        if dependency.modname == modname:
            raise ValueError("Dependency has already been registered: %s"\
                             % modname)
    DEPENDENCIES += [Dependency(modname, features, required_version,
                                installed_version, optional)]