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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 parang (hourangle, declination, latitude):
 """Calculate the parallactic angle of a sky position. This computes the parallactic angle of a sky position expressed in terms of an hour angle and declination. Arguments: hourangle The hour angle of the location on the sky. declination The declination of the location on the sky. latitude The latitude of the observatory. Inputs and outputs are all in radians. Implementation adapted from GBTIDL ``parangle.pro``. """

    return -np.arctan2 (-np.sin (hourangle),
                        np.cos (declination) * np.tan (latitude)
                        - np.sin (declination) * np.cos (hourangle))