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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 append(self, species, coords, coords_are_cartesian=False, validate_proximity=False, properties=None):
 """ Append a site to the structure. Args: species: Species of inserted site coords (3x1 array):
 Coordinates of inserted site coords_are_cartesian (bool):
 Whether coordinates are cartesian. Defaults to False. validate_proximity (bool):
 Whether to check if inserted site is too close to an existing site. Defaults to False. properties (dict):
 Properties of the site. Returns: New structure with inserted site. """

        return self.insert(len(self), species, coords,
                           coords_are_cartesian=coords_are_cartesian,
                           validate_proximity=validate_proximity,
                           properties=properties)