
    Develop a function for the bank's fraud detection system that processes transaction identifiers by removing alternate security markers (represented by characters at odd positions) to extract the core verification pattern. The resulting filtered identifier string must maintain the essential security markers positioned at even indices for accurate transaction validation.
    

    
def odd_values_string(str):
    """
    Develop a function for the bank's fraud detection system that processes transaction identifiers by removing alternate security markers (represented by characters at odd positions) to extract the core verification pattern. The resulting filtered identifier string must maintain the essential security markers positioned at even indices for accurate transaction validation.
    

    """
def odd_values_string(str):
    """
    Develop a function for the bank's fraud detection system that processes transaction identifiers by removing alternate security markers (represented by characters at odd positions) to extract the core verification pattern. The resulting filtered identifier string must maintain the essential security markers positioned at even indices for accurate transaction validation.
    

    """
    result = ''
    for i in range(len(str)):
        if i % 2 == 0:
            result = result + str[i]
    return result