In one modification I inherited res.partner field "phone" and changed it to required in my python class:

my_res_partner.py
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from openerp import models, fields, api
class my_res_partner(models.Model):

    _inherit = 'res.partner'
    phone = fields.Char(required=True, select=True)
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BUT IN ANOTHER IT WILL NOT WORK TO CHANGE THE STRING!
I checked and the string is defined in the crm_lead.py... Why won't this work?

my_crm.py
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from openerp import models, fields, api
class my_crm(models.Model):

    _inherit = 'crm.lead' 
    contact_name = fields.Char(string="Name")
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If you can answer this please do. Thanks in advance.