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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 _get_entity(partition_key, row_key, select, accept):
    '''
    Constructs a get entity request.
    '''
    _validate_not_none('partition_key', partition_key)
    _validate_not_none('row_key', row_key)
    _validate_not_none('accept', accept)
    request = HTTPRequest()
    request.method = 'GET'
    request.headers = [('Accept', _to_str(accept))]
    request.query = [('$select', _to_str(select))]

    return request