pandas.Series.is_monotonic
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Series.is_monotonic
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Return boolean if values in the object are monotonic_increasing New in version 0.19.0. Returns: is_monotonic : boolean 
    © 2008–2012, AQR Capital Management, LLC, Lambda Foundry, Inc. and PyData Development Team
Licensed under the 3-clause BSD License.
    https://pandas.pydata.org/pandas-docs/version/0.20.3/generated/pandas.Series.is_monotonic.html