Builds a string out of a given nested list.
        Args    :
            array   : An array retruned by pyparsing nestedExpr.
            o_str   : Opening str.
            c_str   : Closing str.

def nested_join(array, o_str= '{', c_str= '}'):
    '''
        Builds a string out of a given nested list.
        Args    :
            array   : An array retruned by pyparsing nestedExpr.
            o_str   : Opening str.
            c_str   : Closing str.
    '''
    result = ''
    for x in array :
        if type(x) == type([])  :
            result  +=o_str+ nested_join(x)+ c_str
        else                    :
            result  +=x
    return result