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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 _struct_get_field(expr, field_name):
 """Get the `field_name` field from the ``Struct`` expression `expr`. Parameters field_name : str The name of the field to access from the ``Struct`` typed expression `expr`. Must be a Python ``str`` type; programmatic struct field access is not yet supported. Returns ------- value_expr : ibis.expr.types.ValueExpr An expression with the type of the field being accessed. """

    return ops.StructField(expr, field_name).to_expr().name(field_name)