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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 ofp_ofctl_field_name_to_ryu(field):
 """Convert an ovs-ofctl field name to ryu equivalent."""

    mapped = _OXM_FIELD_OFCTL_ALIASES.get(field)
    if mapped:
        return mapped
    if field.endswith("_dst"):
        mapped = _OXM_FIELD_OFCTL_ALIASES.get(field[:-3] + "src")
        if mapped:
            return mapped[:-3] + "dst"
    return field